Kinda blows my theory that he suicided himself the fridge half-way through the movie...
I too thought it was a decent one-off and was hoping DC might leave it alone, but after its massive $uccess the writing was kinda on the wall.
Small related tangent: I didn't mind Pattison's Batman movie – it wasn't world-changing but it didn't suck either. Farrell's Penguin chewing up scenery was a definite highlight. I've grown to really like him as an actor.