Jeff--With dying or dead hemlocks everywhere, there's ample reason for concern. In fact, a fellow in a logging truck was killed by a falling tree in the Nantahala Gorge a week or so ago. I don't know that it was a hemlock, but that's a good guess.
One thing for sure, this year and in years to come trail crews are going to have a heckuva time clearing fallen hemlocks, and if a high wind comes up I'm seeking woods where there are no hemlocks. If it is windy day, I'll wait to fish some other time. I've already been on three or four streams in WNC (inside and outside the Park) where fallen hemlocks make movement upstream an exercise in extreme frustration.