I doubt FF13 had nearly the negative impact on the series in Japan that some people are claiming.
FF13 was pretty well liked over there, for one thing. The spin-offs were different styles, as well. If people didn't want to play them then they just ignored them.
As the numbered Final Fantasy games are usually unique worlds with new characters and game-play schemes, previous versions will have less impact on subsequent versions and the spin-offs even less.
People are just going to have to face the fact that a large number of consumers simply didn't have much interest in FF15. Square tried hard to make FF15 into an amalgam of things that are popular in Japan instead of being FINAL FANTASY and I think it backfired.
Final Fantasy 15 isn't very Final Fantasy, which is really what hurt the game the most.
