Surface Pro 4

I wonder what proc they will use. I doubt the Cherrytrail successor will be out by then, and I'm not sure it has much advantage over a Core M, maybe better battery life. But seeing how crappy Cherrytrail has performed on higher resolution tablets makes me hope they do go with Core M.

The surface 5 (non pro) is a mystery, I don't think anything has been leaked on it at all. It's possible MS will just let it die, and the new "non pro" version will be the entry level M3. But at this point your guess is as good as mine.

The surface pro's seem to keep a decent resale value. I would keep it for a bit. Either they announce a surface 5 and you are still selling a "pro" model which should retain some value because of that "pro" moniker, even if it doesn't mean much. Or they never release another pro model and you will have to wait a long time for the surface pro 5.