Is the .Net 4 Framework going to change before the "go-live" or can we safely assume that the framework will stay the same as it currently is in the Release Candidate?
I would be surprised to see any significant new features or API changes - but I'd expect some bug fixes or performance improvements. To put it another way, I would still put any software you're building through a fairly rigorous test run after the release, but with the expectation of it still working.
Assume stability. At this point, significant changes would have to be rooted in a design desaster. You basically talk of fixing critical issues at this point. Even IF the api changes, it is going to be minimal.
You said it yourself - Release Candidate
. This means that though large changes are unlikely, they can occur as can small changes.
Framework 4.0 (and VS 2010) release candidate is available under a Go Live license which, amongst othre things, includes "committed to providing a smooth upgrade path from Beta 2 to RC and then to the final release (“RTM”) of Visual Studio 2010 and the .NET Framework 4" and providing support should things go wrong.
Meaning - the API might change (unlikely) and if it does, and it causes big issues, you can enlist MS Support to help.
All things going to plan it should be very smooth to start using RC now and move to RTM when required.