4.6a Beta 1 (4.61.0.3169) will ship later this evening or early tomorrow.
To update to Beta 1 when it ships, use the Update Now command if you’ve switched to the beta channel before, or the Set Update Channel to Beta command if you’re on a stable version (such as 4.6 SR-2). To install Beta 1 from scratch, see the notes and download links on this thread.
Release Notes