Del Potro is reasonably healthy again and Tsonga has looked pretty good at times. Those would be the other two I would say are reasonable choices for who is in the semis along with the usual four.
What about the other top seeds?
Soderling? It's been a while since I've thought so little about someone ranked #5.
Ferrer? Interesting, but doubtful. He does play reasonable on hard courts.
Monfils? More likely than the previous two to end up in the semis.
Fish? Maybe. Quarters at Wimbledon is a decent showing.
Those are the only other two I would put any weight behind being in the semis or finals.