Honestly, I'd like a new companion. Maybe someone besides a youngish british woman from modern earth? As much as I like companions like Rose, Amy and Clara, a little variety would be nice. If they absolutely need to be similar to other NuWho companions, I'd hope they'd at least go for a Donna type companion, a bit older and not going to fall for the Doctor. Or, go old school and go for an Ace type companion. A younger companion who The Doctor is kind of a mentor to, but who doesn't just unquestionably follow him.
Basically, I'd hope the mold could at least be stretched a bit, even if they aren't willing to break it. Heck, I'd also like to see a 2nd Doctor style guy/girl companions, but ones who aren't romantically involved with each other. Basically, I just hope they do something a bit different, and don't just replace Clara with more of the same. Not that such a character would be bad, but some more companion variety would be cool.