Let's assume Rondo signs an extension for $6 million, Powe for $2 million (very optimistic scenario). Pierce stays. You let Ray Allen walk for nothing, ditto for BBD, House, Tony Allen, Scal, Bill Walker, etc. and you sell every draft pick (or don't sign the rookies).
You'd have around $52 millions commited to Pierce, KG, Rondo, Powe, Perkins and Giddens - 6 players. The salary cap for 2010 is projected to be... $55 million.