I think/hope this is the plan. Using Wallace's contract as expiring filler, along with young players/picks, to land a legit talent to upgrade the starting lineup.
I'm not yet convinced that Amir Johnson is the team's starting C. I think he's the starting PF. I love Crowder, but if an offensively minded wing threat becomes available (whither Toby Harris?), I wonder if Ainge would consider consolidating assets for him.