I mean you have to think it gives him some incentive to stick around. You basically get the talent and personalities that you want to coach. Now that those guys are basically loaded on your side of the ball, starting over as a head coach somewhere has to feel a little depressing in some aspect. I don't think he just has this pure desire to be a head coach again, otherwise he would have probably done that by now. We will always be at risk though if the right opportunity and front office comes calling. Let's just hope that doesn't happen.
Yea Seattle is probably the biggest risk but they've built a pretty solid roster so they should be competitive and Carroll will probably stick around a few more years, and who knows, maybe by then we've won (or at least made) a Super Bowl, maybe McCarthy is gone, who knows?
But over the last two offseasons damn near half the teams in the league have hired new coaches so it'll take a lot for him to leave, and it might honestly just be Seattle given his relationship with ownership and the front office there, although there's rumblings the team could be solid within the next 2-3 years.
Supposedly he has a great relationship with McClay and he's basically operating as a de factor HC on the defensive side, McCarthy seems to barely stick his nose in there, so ultimately he probably will hang around for several more years unless the picture perfect opportunity comes open, which might very well just be one particular job.