Mercs in RE5 on PS3/360 had deathmatch in addition to team death match (co-op).
Mercs on iOS has deathmatch in addition to team death match (co-op).
I assume that we'll see the same format in this one. It's just an arcade type game ... it's not like a locked-down save in Resident Evil 1,2,3,Code Veronica,4 or 5 that won't allow you to go through the adventure again a second, third or fourth time.