Estrada's not going to start unless there's a ton of injuries. As it stands, the rotation is:
Dickey
Buehrle
Stroman
Hutchison
Happ
AAA/bullpen(starters only):
Sanchez, Norris, Nolin, Graveman, Francis, Hendriks(Francis will not likely see the rotation, as he's AAA filler.) Hendriks is a tough call.. he's out of options, though he might clear outright waivers.
Of course, there's still the chance Happ is traded.. we'll see what happens.