If you ask me those service packs are only attempting to make up for a poorly implimented and rushed OP system which Windows 7 is not. I predict zero service packs will be needed in the first year, only updates.
The reason XP needed so many was because it lived longer than it was ever supposed too and the security was downright terrible, and Vista,... that Op system needed so much help because it was not tested properly so the service packs were an inevitable part of it's evolution.
Windows 7 has no such problems and the few problems it does have mostly seem to be related to driver
development which is typical for any new Op system.