For arguments sake, lets say Chip Kelly doesn't think that Foles is his guy. What do you think you could get for Foles? Selected 88th overall. Cousins is largely thought to be the most sought after backup in the league. There is a strong argument that you would want Foles over Cousins as Cousins has a very small sample (admittedly, I think most of us would take Cousins).
I would think you could get a 2nd rounder from someone for him. Especially if at pick 40 a team has missed out of "their guy." At the very least you could absolutely get an early third rounder.
The 2012 draft will likely go down as the best QB drafts in a "Bill Walton" EVER. Looking from the 2nd-4th round, Foles and Cousins look promising; Wilson looks like an elite QB; while Osweiler was backing up a pro bowler. In 2011 2nd-4th round has Kapernick, Mallet, and Andy Daulton. 2010, Clauson, McCoy, Kafka (fairly eh backups)
At least in recent years, in rounds 2-4 it appears that you have roughly a 1/3 chance of getting a fine QB, but lets call it a 1/4 as 2012 and 2011 were so stacked. Likewise, you simply can't win a Superbowl in the modern era without an elite QB (Trent Dilfer was not elite, but had arguably one of the best defenses to ever play the game; if you want to argue about that, we can say if you one of the best defenses around a fine running back, and an average QB you have a 7% chance at winning a ring).
I would make the argument that if the Eagles and Chip Kelly see anyone they like in rounds 2-4 they get them. I would even take two quarterbacks. Likewise, I would argue that the Eagles should still implement this strategy even if they keep Foles as he is still an unproven commodity; especially in Kelly's system. Inversely, if you don't see any potential QB's in this draft class trade every pick you reasonably can to get your guy in 2014. This is Philadelphia, the goal is a ring, not a 9-7 season or a 10-6 season and a first round playoff exit.