Assuming he's healthy, St. Louis may be forced to deal Gunnarsson before the deadline. Dunn's emergence has made him expendable, though he's still an effective shot blocker. If the Blues were competing well this year, I'm sure they would keep him as quality depth, but at this point he's a luxury they can't afford.
They would probably be more inclined to trade Bouwmeester, but (a) he has a NTC, and (b) his recent play wouldn't get much interest anyway. But, as a bottom pair guy, a little retained salary might entice someone.