I asked a similar question some time ago. One of the last responses from the core team suggest a way to implement this, but I guess someone will have to pick it up.
I don't think we have to solve the general case of allowing tuples to conform to protocols to get this into Swift. Based on the reception from members of the core team on my thread, I'm sure a proposal will go through like a breeze as long as someone is capable of producing a working implementation.