The real reason franchises got dropped over the years is that each generation has made developing a game a longer and more expensive process. Back in gen 5 Squaresoft flung out FF V, VII, and VIII within a year and a half of each other while juggling other projects like Parasite Eve and Xenogears. These days the much larger Square Enix struggles to make anything other than Final Fantasy and the occasional Dragon Quest; most of their other titles get farmed out to a subsidiary.
Granted S-E is an extreme example--that's why I picked it--but most developers show similar trends. I conservatively guestimate game development takes five times more man hours than it did fifteen years ago. Developers pick their most profitable projects and go from there.
This is one of the major reasons I think the AAA game market is in the process of imploding.







