The OP really doesn't make any sense. If the next movie comes up short, somehow you'll retroactively feel different about the last movie?
Many do about Insurrection, because Nemesis sucked. Although it did well, and was not bad, somehow Insurrection is believed to be the end of it all. Heck, there are even some extremists who now say that the first season of TNG was the beginning of the end.
If the next movie sucks and fails, you'd be surprised about the backlash against this movie in retrospect.