French Open: I can only see Tomic going no later than the third round here.
Wimbledon: Grass is his best surface. Hopefully fourth round or the QF's.
US Open: Third round.
It's impossible to predict these accurately, but Tomic isn't going to have a "breakthrough" year. In fact, I can't see him winning any ATP tournaments. I have high hopes for him but 2013 won't be a noteworthy year. Hope I'm wrong.
You do realize he won Sydney a few weeks ago?
Anyways, it all depends on the draw; impossible to predict these things without the draw.