I imagine they could easily swap out Smith's face with that of the new Doctor. That's what they did when Peter Davison replaced Tom Baker. They'd just gone to all the trouble to come up with a new opening title concept. They weren't going to ditch it just because the lead actor changed.
Frankly, there have been so many changes in the last half season, I'd like it if some of them stuck around a little longer for me to get used to them, even if Smith won't stay. (I'm still having a hard time wrapping my head around that. I was convinced he'd at least stay for Season 8.