Maybe for Vasaell. Johnson is a mediocre shooter and bad defender.
Trading Cade for anyone on that Spurs roster (other than Wemby, which obviously won't happen) would be a mistake. I guess three first round picks is cool, but with Wemby in the picture, those would probably be late first round picks. You guys also have no shortage of picks. Need to start developing guys, and that means holding them beyond their rookie contract.
What the market says Cade is worth, you pay him. If that ends up being the max (hopefully not supermax), so be it.