It's not the relink that will be the issue. Rather, I believe they have some 2GB limitations in their heap management, and to fix those, they might need to rewrite their heap code. That can be tricky, especially if you're using external libraries (Firefly?) that you will need to use the new heap. I've been involved in this kind of work before, so I know it's not impossible. It's just complex enough that as a developer, I would tell the marketing guys that it was too risky to do in a service pack.