I've just seen that Microsoft has given Software Update Services (SUS) another lease of life, and has announced an extension to the end of support date - July 10th 2007. The idea is to give customers more time to migrate off of SUS.
Additionally, a beta version of the next release, WSUS 3.0 is available for evaluation. WSUS 3.0 is expected to be released "in the first half of calendar year 2007." That's MS speak for sometime in late June. I'd bet that the announcement will take place at TechEd on Orlando, but that's only my guess and it not a commitment from MS! You can get more information about the WSUS 3.0 beta 2 at http://www.microsoft.com/wsus