Final Fantasy 7 brought Final Fantasy mania to the world.
Final Fantasy 8 killed Final Fantasy Mania, weirded everyone out, and put the series on a declining trajectory.
SE probably doesn't want to remind anyone of its existence. At least that would be my motivation if I was SE :P
That's really silly. FF8 was actually one of the most popular in the franchise, and the franchise was still incredibly popular when X hit. It was around FF12 where the hype for the series began to die down, and while 13 sold better than 12, it didn't reach the heights of FF7, 8, and X.
The most likely reason is that next year is the 20th anniversary, and it makes more sense to announce it then rather than now.
I describe myself as a little dose of toxic masculinity.