Saul will never be able to be very successful following the events of BB. He was a very public figure back in Albuquerque with billboards and commercials and his face everywhere. If he became a bigshot elsewhere, even Nebraska, somebody would recognize him and he'd be tied back to Walter somehow. At the end of BB, everybody was bailing on anything connected to Walter: Mike, Saul, Jesse, everybody.
No, Saul will be managing a Cinnabon for life.
Why can't he go to a Country without extradition?
Why is he stuck in the USA forever?
Go to Canada? Mexico? Europe?
Some exotic Island where not too many questions will be asked maybe?