They definitely can't afford Deni lol. He's on a great contract 2 more years and then he'll likely get a Max Deal from Portland (assuming their goofball owner doesn't low-ball him too). Either way, he's going to get paid max money by someone in a couple years.
Spurs already have their core big money players on the roster with Wemby, Castle, and Harper (and Fox...for now). That's our big 3. Now it's just a matter of developing them and keeping the supporting cast around those 3 stacked up for the foreseeable future and replacing role guys like Devin, Champ, Kornet, Barnes, etc. as needed.