I'm not a sadist or anything but...I really thought 3 would've been a perfect ending (love or hate, really) if the toys were incinerated at the end (that's not sarcasm...i loved the movie and saw it 4 times in theaters)
I only saw Toy Story 3 about a week ago, and I agree it was the perfect ending to the series. Another one is not neccessary. All this spells, is there only looking to cash in on the franchise, as people will go in droves to see it.