John,
Whether there will be a VFP 7 exam or not I am sure will be directly related to how many people take the VFP 6 exam. The best way someone can insure the existance of a VFP 7 exam is to take the VFP 6 exam, simple enough.
As for MCSD, well again the cert will expire one year from the announcement of new criteria. New criteria will be announced related to the exams for the new products. I think you 2002 estimate for new exams is probably a good one. That would put the cert expiration in 2003.
As to whether a VFP 7 exam, if there were one, would count as a core exam or not is guessing at best. There may even be a new cert for MCDNSD (Microsoft Certified Dot Net Software Developer) for all we know, with its own set of core exams.
While I agree that asking questions now is appropriate, I don't believe that anyone should be reluctant in taking the current exams now. Any cert they achieve will be good for at least 2-3 years maybe longer.