Sun just publicly announced the Early Access 1 program for Sun Ray Software 5 beta on the community SunRay-Users mailing list (at http://www.filibeto.org/)! Key features listed in this EA are Adobe Flash enhancements for Windows sessions, Windows Server 2008 support, and a new Sun Ray Soft Client. The announcement also mentions that EA2, due later this summer, will feature USB redirection for Windows sessions.
While it's not Adobe Flash enhancements for UNIX, it still sounds like an exciting release which I will be sure to test!
The program officially starts at 3:00pm EDT today. Details and the original announcement can be found here.