Confirming his famous Doctor hairdo (sported by the banana above) will be making an appearance in spite of his current shorter look, Matt Smith says:
The coif will be there for the finale in some way, shape, or form, but I think it could be quite funny to have the bald hair. I think you could have, like, that MACaulay Culkin scene in Home Alone when he, like, slaps on the aftershave - I think the Doctor could sort of wake up and be like, 'Ah!' I'm sure Steven will come up with something. He'll come up with something clever.
Source: Contact Music