There are a number of great answers out there that have never been accepted as the answer for whatever reason. Would a new feature that allows high-reputation users to vote to accept the answer after a certain time period has elapsed be helpful?
I'm not going to argue for any specific reputation level or time period, but I would throw out 30 days and 3000 reputation. If, say, 3 users with voting ability vote to accept the answer, it gets accepted.
It seems to me this would be helpful in that readers would have more assurance that the answer was super solid. I realize that the number of upvotes gives some assurance, but that green checkmark means something, or else it wouldn't be there to begin with.