What if there are no volunteers to sit in the emergency exit row? I'm currently seated in the emergency exit row, and had an interesting thought. If I was unable or unwilling to assist the crew in an emergency and operate the emergency exit, then I am supposed to contact a flight attendant to be reseated. 

But the emergency exit row sucks. The seats don't recline, there's no under-seat storage, there's not even tray tables. What if nobody volunteers to switch seats with me? Will I be rebooked onto a different flight? Or maybe will someone be forced to switch seats with me?

(Let's assume for the purposes of this question that I am physically unable to operate the emergency exit, say because of a broken arm. Let's also assume that the flight is fully booked and there's no empty seat that I could be moved to.)
The government requires any passengers seated in an exit row to be 15 years of age or older, be willing to assist in an evacuation and have no limitations that would prohibit their assistance.


Source: United

I.e. you won't be given that seat if you can't assist or unwilling.

Personally I always request an aisle emergency [exit] seat near the window. This way the bulky slide is out of my way and I get plenty of legroom. I'm very tall, legroom matters. You'll always find someone willing to switch if they're tall. What I'm saying is, this seat that you hate, others love.

But in your very specific hypothetical scenario of a full flight and wrong seat and unwilling passengers, the government says someone must switch. If the issue causes too much trouble, then someone (who is causing the trouble) will be escorted off the plane more likely, freeing up a space...

... to be immediately filled by someone from the standby list who doesn't mind sitting in the exit row. voretaq7

Have a nice flight.