I think he should hit 5 anyway.
If the gods are with him, and not with anyone else, then he might hit 4.
I'm anticipating a couple of good Grand Slam runs, followed by a bit of a fade towards the end of the year.
I may, of course, be deluding myself .....

.... but then, my predictions for 2008 included less than half of GSs and Masters being won by Rafa and FedEx, which seems much more likely now .... muahaha.