Buttler in T20s, no. Bairstow it's a close run thing, Morgan plays a different role to Hales so not a like for like swap and Stokes (as a pure T20 batsman) I don't think has shown he is the match of Hales at international level.
There's an argument that Stokes is wasted at 6 which is not without merit. Not sure it's the most sensible selection but I would love to see them experiment with Buttler, Stokes, Hales and Bairstow as the top 4. That said, I've still got a lot of time for Roy and Malan hasn't done a lot wrong either.