First off, if this is a possibility, it won't be until AFTER the Colts are 100% on Luck (either sign him or actually Draft him).
The assumption is to get RGIII
Vick is good, but neither youthful nor durable (so a backup won't be riding the pines all season). I can't see any team of Andy Reid's NOT having a QB that can run like a RB. He's got to be scheming on how he can get him. Plus getting him would have the side-effect of not letting the Redskins get him.
The Eagles have the 15th overall pick, and double picks in the 2nd and 4th rounds, and triple picks in the 6th. I'm also not 100% sure they want to keep Jackson long-term (just a feeling I get).
In short, I think they have the motive and the ammunition to get a deal done. And the thought is somewhat unsettling.