No idea. I don't buy that St. Louis is going to walk all over anyone though. Toews can easily say no if he wants and Hockey Canada will be happy that he even answered he phone call. Keith is in the same situation, but he did agree to go after Chicago's first round exit in 2012. I would say slight chance, though his personal situation is different now and he does have another tournament looming later in the summer. Seabrook would be decent, but there is no history of him participating. I believe he got married in the summer of 2012 when Keith went.
There is lots of interesting potential among defencemen who may lose out in the first round. For instance right now San Jose and St Louis would play in the first round. That could yield Pietrangelo or Burns, with both in tight to make the roster for the other tournament later in the summer. Could be good.