Lot of love for Junius right now, it appears.
Let me throw in my two cents:
Right now, Coston's value comes largely through potential. Yes, he has improved since being drafted, and has had flashes of excellence. But he hasn't shown enough yet to win a starting job at the team's weakest position.
And how does a guard drafted this April offer value. That's right. Through potential.
I'm not enough of a draftnik to know what the potential in the 2nd-4th rounds are for OG. However, I can see an expert in drafting (i.e., Ted Thompson) looking at that potential and saying, well "those flashes" aren't enough. I mean, he decided that Will Whitticker didn't have enough potential to even stay on the roster after 15 games; he could well decide that Coston hasn't shown enough in 16 games to prevent another high pick for a guard if he sees more value in what he expects to be available at that pick.
He could even decide that Coston offers no more value than a later round guard, than the next Barbre would be better on a roster where that higher 2nd pick Coston yields gets used for a OT, CB, TE, or whatever.
It really depends on how Ted views the relative potential of Coston and guards available in this year's draft compared to how other GMs view that relative potential.
What leads me to be skeptical of the Coston part of this scenario going down (I really think deMulling is a separate issue) is that I have a hard time imagining another team valuing Coston more than Thompson does at this point.
I for one wouldn't mind if any current guard were traded to move up in the second round. Because, as I think everyone has figured out by now, I don't see any of our current guards (with the possible exception of Barbre) as particularly valuable. Heck, package two of them in the deal if you want.

But I'm also pretty sure that Ted sees those same guards as much more valuable than I do.
And, my gut tells me, much more valuable than the other 31 GMs see them, too.