I keep hearing this, but it ignores two things: 1) A ton of teams are going to have significant - max cap space and 2) How many players of or at least close to the caliber of Aldridge, that fit their primary needs (if Green is re-signed, that leaves starting PF and sixth man) will 1) Leave their current team and 2) Do so to come to San Antonio. In other words, it's probably Aldridge or bust, not just for now, but the near future.
As far as what will happen with the roster if he doesn't sign: I'd expect everyone other than Belinelli, Bonner, Ayres and Williams to be retained. They'll probably sign Teletovic and Delfino (depending on his recovery) or Jenkins.