No clue if it has ever happened, but you can bet your ass that if Wilson and Wagner both played on an East Coast team, ESPN would be debating this very question as we speak.
Unfortunately for us, it doesn't really fit in with the media narrative for Seahawk players to win awards like that, especially when there are mega-hyped players like Luck and RGIII, so I just don't see it happening. Because honestly, Wilson should be the frontrunner right now, but instead he is a distant 3rd. (hell, or even 4th - don't put it past the East coasters to talk up Doug Martin over Wilson)
Wagner should probably be the front runner too. Who are you going to give it to over him? Keuchly? He has a few more tackles, but less impact plays. The only reason he has more tackles is because he plays on a worse defense that is on the field more. I'd give it to a leader on one of the best defenses (with big stats too) like Wagner. But again, Keuchly plays on an East coast team, so that alone should propel him to the top spot if there is any question.