Re: Wishful thinking
I doubt it will end there. He'll never be able to travel to the US, ever. And it's likely that if he moves to another country they'll try again there.
In effect, he's confined to the UK. He can't even holiday somewhere unless it has a non-extradition treaty with America and unless he can be sure his flight won't be diverted enroute. As soon as he sets foot in a different country, the Americans can try again, as you suggest, and I'd imagine they probably will.
While that is undoubtedly very limiting, particularly these days, I'd imagine its a lot less limiting than a cell for 90 years.