This is all assuming that Obama decides to actually 'obey the law' for once in his term.
While I like the clock in the sense that it will force the question, I do not trust Hussein to abide by any American laws or traditions. Day by day he is increasing his power and shrugging off Congress, SCOTUS, and the American people.
If Obama decides to actually leave, that will be great. But there is too much time between now and then to predict what he will do with his remaining time. And it could be literally anything, since he has no constraints at all.
For me, myself, it is much too early to start celebrating. When I see him gone, only then will I believe it and allow myself to feel relief.