Lurker they could shed contracts to make space for him if they really wanted....
Ben Wallace is going into retirement and either way his 14 million dollar contract is up at the end of the next season. That will free up space. They also could easily shed Z if they wanted (his contract is up in 2010). Wally's contract is also up as well. Plenty of teams have been going after him for that reason. They have PLENTY of options and would have space. Even with out getting rid of guys like Mo Williams, Delonte West, and Vallejo. Wally, Z, and Wallace were DUDS in the Orlando series.
IF he is fully recovered and IF the Spurs can compete for a title as two big Ifs to go off of. I am merely suggesting an alternative.
As far as the Spurs rebuilding, adding young players is one thing, building a championship team out of them is another. They haven't really replaced Bowen (at least fully) Duncan (not that they will but somewhere anywhere in the same ball park as him) or Manu. Thankfully Parker is still very young.