Even though we're playing well enough to be in the mix for playoffs, I don't think any moves should be made too hastily. Smart still has 2.5 years on his deal and we don't know what he definitely can or can't be yet. At this point you wouldn't even be selling high, so why not keep him around? I have my concerns about his durability and ability to improve his shot, but what could we realistically get for him now anyway?
Keeping Smart, Thomas, and Bradley in the guard rotation should keep them happy enough for now. In another year or two, maybe one will want to be the unquestioned starter but we're not at that point yet.
As much as Isaiah needs to be hidden on defense, Smart is a liability on offense. Since we really lack offense right now Thomas is looking to be more essential, but that may not be the case in the future. At some point Smart has got to at least be able to make an open jumper consistently though.