Well, there has to actually be a vacancy. Maybe there will be, but I'm not sure Staley is going anywhere and the Rams don't have a first round pick to trade, so a Payton trade to either LA team isn't looking likely at this point.
If the market ends up being dry for Payton, that could be the scenario that gets him back to New Orleans if, in fact, that is a possibility he is really considering (and assuming the job opens back up for him). I would just be concerned he could see that as an opportunity to finish out his contract here and then be free to go wherever he wants when the right job does open up, without the hurdle of having his rights negotiated. Much easier for him to make a move under those circumstances.