I am a huge Law fan, but I doubt he will try anything as drastic as creating a "Room" that can engulf the entire bird cage as it had already take alot of him to create that last extremely large room he had made. If he does anything along the lines of using "Room" and "Shambles" to save anybody, I foresee it happening when everyone is bunched in together, make a moderately sized "Room" then just start using "Shambles" to move people to the other side of the cage, and quite possibly leave Doflamingo to be killed by his own technique. But that last little bit is highly unlikely, as Oda has been leading up to Luffy being the one to kill him.
But it would be nice to see Law get that last little bit off and be the one to ultimately kill Doflamingo.