They are clearly not in any rush to promote anyone from Worcester.
Valdez is likely demoted today once they officially activate Grissom. Hamilton will probably be demoted when Gonzalez is activated.
Cooper is really a bland journeyman, but will probably be the primary stopgap 1B until Casas returns or he plays himself out of the position. And given the leash Dalbec had with the role, that could be a while even if he struggles.
As for those last two 40 man roster spots, most likely they are monitoring the waiver wire for arms. I suppose they could claim Aaron Hicks and become the next team in line to realize this guy is just not going to ever play up to his potential. Or see who Houston DFAs today when they clear a spot for Joey Loperfido. (The Astros have a few borderline pitchers like Dylan Coleman, Blair Henley, Joel Kuhnel and Parker Mushinski that Breslow might like more than Houston does. But I suspect the Stros DFA INF Trey Cabbage, who is far less interesting beyond his cool name.)