Wow! A coherent and rational post. Proud of you my boy! You seem to be assuming that states that impose new bans on same sex marriage will invalidate existing marriages and you might be right.
My guess is that some states would let those marriages stand but it seems likely that some would seek to invalidate them. Now that would be chaos, and cruel. Would this court consider the way in which they could upend so many lives? I would not bet on it. I suppose that they could include a provision that the states cannot ban the marriages retrocativly, but again, don't bet on that either.
In any case, many people who wish to get married in the future would be shut out. If Obergefell is overturned, their only hope would be the pssage of the Respect for Marriage Act which would require states, through the Full Faith and Credit provisions of the Constitution to allow people require states to reccogognize marriages from states that allow gay marriage, but even that has its pitfalls.
Such a provision would most likely be challlanged up to the SCOTUS with an uncertain fate.
States may have residency requirements inorder to get married, so a couple from Misssisippi may not be able to just waltz over to a free state and then go back home as a mrried couple