The Spurs shouldn't make a major trade for anyone under 28. Yes, under, not over.
scott got me thinking about this a while back, but it's foolish to try to get Wemby a young running mate, especially one on a max contract. As
exstatic has been hinting at, Young is just going to get more expensive as time goes on. The Spurs shouldn't look at trades with the idea that those players will be on the roster five years from now. They absolutely need to have a long-term view on the implications of their deals, but that's really in terms of the rookie-scale guys or long-term non-max guys like Vassell and maybe Johnson.
I think you can make the argument that the Spurs shouldn't lock themselves into Young until/unless they believe Young is going to put them over the top. Likely a Wemby/Young duo is still a major piece away from being a real contender for a few years, and that piece would be hard to get if they're trying to make a deal now.
The team should pursue a legit vet this off-season. Not a young vet, and not a cast-off. They should get a guy who can show them how to win. I've already said all this before, so I'm not going to go into much again. But ultimately, the Spurs should probably pursue a guy who's at the peak of his earning potential and be willing to pay him the money they aren't paying Wemby right now to chaperone the team for a couple of years. Then when it's time for Wemby to be the star, they have that money free and can make win-now moves, and that old guy can hang around on a cheap deal if it still makes sense.