Personally, I think he will go to Arsenal.
Man United is a poor team which may not be in Europe next season, wastes money and it has a lightweight CEO. Non-starter in my view.
Man City also needs a rebuild, as the team is ageing and I doubt he wants to turn over ten players in the next year. Familiar executives, but he is a cosmopolitan guy and cosmopolitan means London.
So I guess Chelsea or Arsenal.
Chelsea is Mourinho's team and he won't want to inherit it, win stuff and have the Portugeezer take the credit. Also, Chelsea isn't likely to be in Europe next season and Guardiola is not going to waste a year watching lesser managers compete.
Arsenal makes the most sense. All the ducks line up.
Wenger will think Guardiola's Arsenal can take the step up to win the Champions League. He will want to bow out as Premier League champion, having proved everyone who doubted him wrong, leaving the next occupant of the managerial seat a brilliant, flexible, skillful team reaching its prime, a new stadium paid for by his own careful stewardship (Wenger's greatest reason for pride) and robust finances.
Guardiola will want to build on top of the firm foundations that Wenger has built. He will see that Arsenal gives its managers time. He has already said he admires the way the club is run. He wants to make history at this stage - money is something he is guaranteed wherever he goes. He will probably think his pressing game using Wenger's team can win the champions league. I think so too.
All the folks thinking backwards think otherwise. Looking forwards, Guardiola is going to see Arsenal as his best choice.
I think he will go to Arsenal and Wenger will join the board. Beyond a doubt, Wenger is Arsenal's greatest manager. I would add an accent to the team's name in his honour.