people hate v, people hate viii, people hate ix, people hate xii, people hate xiii. the fact that ff's are so different from one another is what makes them great to me. it just sounds like people want the next ff to be like [insert fave ff here]. and if that happens to be x-2, or xiii-2, then you have bad taste or something.
I agree however I think the reason it's so bad right now is because we always had another Final Fantasy to look forward to if the recent one was a disappointment. I don't think XIII would have this much vitriol towards it if we had just gotten it and moved on to XV. Instead, we got two un-needed sequels and still no new mainline.