I can entirely see it, because I CREATED the "How Soon Will the Backlash Start" thread. When people are comparing TDKR to SM3 or B&R already, and yes there are fans who did, it is inevitable that if BVS is half decent, it will become a major chorus. Not unlike how so many were trying to put down the Chris Reeve films or (hilariously) claiming that Shannon was better than Stamp only a few months ago.
However, I do think these films will endure past that initial and petty backlash. In another ten years, they will still be masterful and rediscovered by the fan community while the film community, critic community and GA already considers them fantastic.
And for the record, while third one is probably the least satisfying for comic book purists, I increasingly see it as the second best movie in the trilogy and one of the five best in the genre.