I think host migration is probably a very difficult thing to accomplish smoothly.
Think about it, if the host is in charge of even just basic game information, such as time remaining, and that connection is suddenly lost, for a legitiamate reason. How does that information get passed onto the next console, and how do you choose to pass to?
Since you don't know when the drop is going to happen, you either need to always be ready at a moments notice, or have a outside server to manage the transfer.
And even in the best case senario, there will probably be a pause as the transfer is made, which may still mess up the game.
tl;dr: Host Migration is a great idea, really could help games continue if the host disconnects for any reason (don't always need to be cynical), but it's not an easy task.