I was almost immediately let down by L4's introduction, even at the same time I was excited about getting the Portfolio. Others couldn't praise L4 often or loud enough...while I was desperately looking for any reason to like it. I really did want to like it, but just couldn't. It simply didn't do then...and still doesn't do now...what I use L3 to do on a daily basis.
Others have discussed what L5 may be, but I want to throw out a few suggestions of what L5 needs to have included for me to become a happy adopter. I would love to really, truly WANT to say goodbye to L3 when L5 is released, but I must have certain features to make that move.
1. Window History menus--This feature of L3 is unexplainably absent from L4, and I am flummoxed by its absence and the lack of outcry to get it added. I use this feature CONSTANTLY in L3 because it is highly utilitarian in a software program where hotlinks are the "raison d'etre". I can whip through 10-20 Bible hotlinks in less than 5 minutes.
With the drop-down Window History menu, a list of the last 10 page views in a given window is shown going both forward and backward. It shows me my track of hotlink-induced inquiry, allows me to backtrack to precisely where I want to go with a click or two, rather than blindly backtracking until I find the view I want. This is very much like the IE Forward and Back buttons...they used to have the "down" buttons that showed the history, but now you just right-click the back and forward buttons to display the history menu. I prefer the down arrow, but either is better than neither, which is what L4 provides.
This is a fundamental and super easy feature to include...please make sure L5 has this. 
2. Next, and this is super important for me...I really, really, really want MY Library to have a nameable drag-and-drop folder/subfolder sort feature. When I open my Library and have over 4,000 lines of items, I get depressed rather than excited, and that's a shame. Don't get me wrong, I'm happy to have Perseus, and Portfolio, and the hundreds of other items in my Library, but the volume is daunting in the extreme. Please...don't tell me I can create and use Collections...they don't do what I want (I'm NOT concerned with searching at all in this regard). I want VISUAL control of my Library, in much the same way I can choose upon which shelf I can put a book in my hardcopy collection. Of course, being digital, there can (and SHOULD) be greater flexibility in my folder/subfolder grouping ability--for instance, I should be able to have one book appear in 2 or more subfolders simultaneously (i.e. an author folder and a lexicon or language or theology or commentary folder, or all of the above). This would have nothing to do with physical location on the disk, obviously. My main goal is to be able to open MY Library and have my over 4,000 resources show as approximately a dozen folders (named and sorted as I choose). I could have one folder labeled Perseus and in that folder all 2000+ items would reside in perhaps 4-6 subfolders (Greek, Latin, English, etc.) without visually clogging my Library and dampening my spirit. One thing I like to do is LOOK at, literally visually peruse, my library...organized in the way that I choose. This function would be very much like the standard folder/subfolder ability available in most MS programs such as Windows, Word, etc., including the standard Shift & Control choosing functions for multiple item choosing and moving. As a special request, I would really appreciate it if Logos provided an extensive pre-formatted collection of folders and sub-folders so that I & we (the customer base) didn't have to spend days and weeks creating from scratch our own individual folders when most people would likely want many similar folders. Having one person create in advance an extensive template of folders that can be edited would save tens of thousands of hours of customers having to individually duplicate what every other Logos user will likewise be creating in their own Libraries.
I don't know if the current Library management options conflict with what I am suggesting here, but if there is an issue, then perhaps you could have an A-B switch that allows folders/subfolders vs. the current L4 method, sort of like switching from Windows Classic to Aero. I do think many users would like and perfer folders to the current method, at least sometimes.
3. Notes. This is such an important element of my Logos usage that it is daunting to even think of describing precisely what I want and need...and NEED is the biggest understatement in the history of understatements. If L5 doesn't at least match what L3 does in this consideration, I will likely be forced to use L3 until I die or Messiah returns. I am prepared to buy 5-10 duplicate computers that have OS's and browsers that are appropriate for L3 that will allow me to continue using L3 for the long haul...but I would love to not have to go to such extremes.
Bob knows somewhat how I use Notes in L3...I explained it to him in person. I use my Notes in L3 not just for organizing my thoughts and insights, but for producing PRESENTATIONS. I forgo as extraneous programs such as PowerPoint, preferring to conduct my public studies of Scripture WITHIN Scripture. I make notes within the Bible which include my own selections of related verses, pertinent lexical aid references, quotes from commentaries and monographs, my own comments, etc. These notes in L3 have a distinct advantage over notes in L4--they are not limited in size to only 2.5x3 in. boxes. I can, with a bit of clever manipulation, get Notes pop-ups that are almost as large as my screen. More than any other consideration, I absolutely REQUIRE this ability. I cannot stress enough how flawed the thinking that went into the decision to limit note size was...it is like creating a car that won't get out of first gear for safety reasons. By using Notes in L3 the way I do, I am able to create hotlinked Bible studies without the hassel of hotlinks...a simple mouse hover brings up a plethora of Johnny-on-the-spot info...and mutiple notes can address numerous issues pertaining to a particular text...all while never leaving the Text or having to make a single click. L4 simply can't approach this ability. There are some L3 Notes limitations I would like to see addressed. I would love to have the ability to get Notes that can be pinned (so they don't disappear as soon as the mouse moves off the note icon) and scrolled. L3 has scrollable notes for notes that are longer than the largest window size allows, but only for Logos factory notes, not for notes created by users. Finally, I want much more word-processing capability in the Notes function. I don't necessarily need MS Word, but much more than what is currently available. I know MJ wants tables and charts...picture import would be nice...but more font sizes (i.e. not just 8, 10, 12, 14, 16, etc., but 11 and 15 and 19 if that's what I want/need). Also, please ELIMINATE ALL BUILT-IN DOUBLE-SPACED PARAGRAPH RETURNS. If I want double-spaced, let me hit Return twice...don't think for me...for your ways are not my ways. 
4. I would like more color options for highlighting and visual mark-up (as L3 calls it). I know that L4 has some increased choices over L3, but I don't use L4 for Note creation so I'm not that sure what is currently available.
I appreciate Logos as a company...you play an enormously important role in the ability Bible students have of comprehending Scripture. What I request here is what I know has become essential for me. I hope you can find a way to include these features in the next major release. Thanks for listening.
