I just saw this over at keznews, and the source article has been deleted so you can take this with a grain of salt. We are starting to see more and more documentation up on MS talking about the RC (there will only be 1 RC so there is no RC1,RC2, etc), and blog postings are showing that 71xx is the supported minbuild number for upgrading to RC. So like I said grain of salt, but with the MS blog posting about the RC upgrade process, I take it that RC is RIGHT around the corner.