Right now, Oakland can't afford a big budget, everyone knows that. Their attendance is shit, and their revenue is very low. However, if they're able to move to San Jose then they would be in a better position to sign players and compete for their division. However until the revenue starts coming in from a new stadium, they aren't signing anyone.
Once you've accepted that it's easy to see the A's have two options:
1) Get rid of Gonzalez, Cahill, Bailey, etc. now
or
2) Get rid of those players right before, or when they hit free agency. Which just so happens to be right about when they should be opening the new stadium if everything goes right.
If you're the A's and planning on opening a new stadium in a few years, wouldn't you want the vibe to be in 2014, "wow the A's have a ton of great prospects ready to graduate to the major leagues," and not, "wow the A's just got rid of all their good players, they suck!"