No, one of them would have to switch conferences and it's been reported the Raiders are willing to if it comes to it. The problem isn't even that they'd play in the same stadium. It's that there would be two teams in the same metro area in the same conference which would be a TV scheduling nightmare with CBS being the league's primary AFC broadcaster which is further complicated by the fact that most all west coast team games are in the 4 PM time slot. The Seahawks would likely be the team from the NFC that switches.
That makes sense. Seahawks were an AFC West team from 1977 to 2001. I hope this happens. No more playing them every year.