Nope, no such thing in Win7 (perhaps this is the reason why there will only be WinX from now on: everything is just an update). There's WU, but nothing about "oh, and we'll force-feed you a completely different OS whenever we feel like it". Plus, the GWX program played fast and loose with user consent; quite a number of people claim that WinX installed without any user action. In other words, that would mean "we take inaction for consent"; way scary.