We need to remember that Parsons, Lin, and Asik are all up for free agency after this coming season, as well.
So, let's say what we are talking about is LarBrd33's suggestion of Wallace and Rondo for Asik, Lin, and Parsons. Then what? Is this purely a money saving move or will Danny be looking to re-sign those guys (at least Parsons and Asik) when they come up for free agency?
Surely, between the two of them, they'll command at least what Rondo will command on the open market. So, we'd save some cap space on Wallace's contract which isn't set to expire until the following off-season, but, on the other hand, we wouldn't have Bird's Rights to the players we traded for. Ergo, resigning them would chew up more cap space than resigning Rondo would.
In essence, we are talking about trading Rondo for Parsons and Asik, two players who would need to get paid, as well (that's what happens with good NBA players--they get paid).
I'm not a fan of the "we can't afford good players" philosophy of rebuilding. Eventually, fans will decide that almost all players aren't worth what they are going to be asking for, and many will want to just get rid of them, keep sucking, and hope for luck in the lottery.
Folks seem to be so worried about what has been termed "the perpetual cycle of mediocrity," but, personally, I'm much more concerned about falling into a "perpetual cycle of suckitude."
In case it's not clear, this is an argument for keeping Rondo, paying him, and using him as our best chip to attract other good players to put around him.