It's a shame to have to wait so long for the next series (2010 :anjou_sad: ), but Steven Moffat is a wonderful storyteller and "The Library" and "The Forest of the Dead", were my favorite episodes. Series 5 is going to be amazing since he is taking over as head writer(bye Russell T. Davies!)! At least we get the Christmas special and a few Doctor Who movies staring David Tennant, to look forward to; which brings me to episode 12's cliffhanger...
The Doctor is actually going to regenerate, but will he stay David Tennant? I think so, and it would be a complete surprise to see otherwise. There are some theories out there as to how his regeneration will get interrupted, thus keeping him Doctor 10.
When the Doctor got shot by the Dalek during his reunion with Rose, the death beam passed through only the left side of his body: hitting one of his two hearts. Since one heart is theorized to still be intact, it could possibly interrupt the regeneration and only heal his torso, leaving his head intact. Sound weird?
Another theory involves the Doctor's severed hand (His hand was cut off in the very first few hours of his regeneration in series 2). The Doctor keeps his hand near the Tardis as a backup generator(his hand contains an incredible amount of energy). Now if you remember, the Master used his hand in conjunction with the Tardis to regenerate himself. So this most likely will alter the regeneration process in some manner. People have said that his hand is going to grow a clone doctor! This clone will be human, and the Doctor will stay the same completely healed. So we might see two Doctors running around? One in his usual stripe suit and the clone in the blue suit!
So what are your thoughts?