Quote: "With the directx 9c thing, will FPSC games still be playable in a few years?"
I am not sure where so many people think they are getting issues with FPSC that they think is caused by the version of Direct X they have installed.
As with most frameworks, including Direct X and .NET framework most things stay backwards compatible.
I have always kept Direct X up to date with the latest version and never get any direct problems resulting in FPSC.
If anything, I had a few issues with GPU drivers when FPSC first started using shaders. But it didn't take me long to sort it out by either fixing my driver or finding another work around.
I think where some get confused is the fact (or rumor, maybe?) that Microsoft may discontinue official support and development of the .x file format.
As for my opinion on rather or not FPSC will eventually break or suffer complete code rot because of Window OS changes in the future:
It could happen, but Lee and the other guys that are involved in the development of FPSC always seem to be on top of everything.
[Edit] Adding To:
Will games created with FPSC NOW eventually be unusable on future OS(s).. almost certainly at some point, but that is the nature of the beast.