You are treating the fact that he has two more years as a negative, when in truth it should probably have a ton of value on the market. Especially at only 5 million and without Seattle being in distress to move him.
Sure, you can get someone younger and under control longer. It won't be anyone who has yet shown that they are anywhere near as good as McCann though. That's basically just a change of scenery trade.
If you use Jiricek as the trade comp for Nemec, I wouldn't even hesitate to give up that same amount for 2+ years of McCann. 1, 2, 3, 4 + Low ceiling but likely nhl prospect? Sign me up all day.