What trilogy curse? There are plenty of great 3rd installments as there are bad ones - Toy Story 3, Indiana Jones and the Last Crusade, The Bourne Ultimatum, The Good, The Bad and The Ugly, Army of Darkness, Lord of the Rings: Return of the King, Die Hard With a Vengeance was at least better than Die Hard 2, and hell, even Revenge of the Sith was the best of its trilogy (not that that's high praise or anything...). And while not the conclusions to one story like TDKR will be, Goldfinger and Harry Potter and the Prisoner of Azkaban are arguably two of the strongest entries in their long respective franchises.
Just because Sam Raimi dropped the ball, Tim Burton left the director's chair, and someone out there apparently expected Brett Ratner to NOT ruin X-men doesn't mean there's a "curse." (And yes, I know there have been other bad 3rd installments, but it always seems to be focused on those 3 whenever people discuss this topic in relation to TDKR. This is the same creative team that brought us TDK, and there's been no behind-the-scenes drama or studio mandated rush jobs. I don't see why this is even a concern.)