Finding another captain from the current crop of England players looks a problem.
There's no one who stands out as 'FEC' in the way that Root and, before that, Sir Chef did when they came into the team.
I don't think that it's something you can land on Stokes when (if?) he comes back.
I'm not sure that Buttler is an option as anything more than a stand-in when needed.
Therefore, for me, Root stays as captain until after the Ashes. Hopefully by that point the team as a whole will have got their act together and the question of changing captain will be moot.