It's hard to think of something permanent in superhero comics. I guess it would have to be something Batman experiences that cannot be un-experienced easily. One thing I can think of is Batman losing his parents again, but this time as an adult. Martha is resurrected and she is killed along with Thomas Wayne.
I'd like to see crazy murderous Martha become a recurring villain just because she was such a cool character, but it seems unlikely.
A wedding would be completely awful, in my opinion. A total story-killer for the ages.