the games are best celebrated by a dying generation. the early ff fans must be in their 30's by now.
from ff7 up to ff12 people have started to forget about the series. so it's really a new audience now.
if they can't make the same impact as they did with ff7 and so on maybe they would be pushed aside and the sales would drop hugely. also the fact that the orginal creators would eventually have to leave could add to this downfall.
the future generations won't even know of the past games, or care for them. i don't think the new ff games can produce the wow factor that it has done in the past.
i give it another 10 years.