, BitFlipper wrote

I think the bigger question is:

If our company spends a lot of resources developing a "cross platform" RIA that is supposed to run on Windows/Mac, will it still run on Windows/Mac 5 years from now? Will it even run on Windows 5 years from now?

That can be said to HTML. Some old pages break in new browsers.

But, IMO, MS does a pretty good job on BC, so, you shouldn't be worried.