I think if Tim comes back (and assuming Manu does too), then the plan would be to do little besides bring over young guys. Maybe there'd be a trade involving Mills and/or Diaw's contract, but I expect nothing major to change in the rotation except maybe Boban stepping in for West as the bench center.
If Tim leaves, I think we may see the team shake things up a lot more. People can keep acting like the Spurs are going into next season close to their 67-win form, but they aren't. They need big changes so that their roster can fit the new system. I can't see Diaw coming back on his deal. Mills might come back, but with no Manu, Patty's viability falls quite a bit. I could see him being dealt. I think the plan will be to find a new bench, since Anderson may be the only returning member from the second unit. They'll probably look for offense, like Adams, though hopefully with more production. They might bring in a vet shooter to compete with Bertans. I don't think Durant is the plan unless he told them he was leaning toward picking them. There's just no coming back from moving Green or even Parker if they are left with no Durant and the other free agents potentially already locked up.