Today Microsoft released the first release candidate of Internet Explorer 7 for Windows XP SP2, could this be a sign that we should see a release candidate of Windows Vista soon? I suppose time will tell.
Given that the previous release of Internet Explorer 7.0 within Windows Vista Build 5472 was 7.0.5472.5 and the RC version is 7.0.5700.6 it would seem logical that the next build of Windows Vista that we see will be at least build 5700.
Update 1:30PM PST – It appears that Windows Vista Build 5700 is a recent build of Windows Vista as seen at Microsoft TechEd 2006 in Australia. See the screenshots at www.joejoe.org and also note that the build is labeled as RC1.