Not sure yet.
Very happy with my S currently, especially since the last update and we are suppose to be getting JB this month, so I will see what the new nexus device(s) bring and what happens with JB on the S.
The only thing, which I want over my S is a bigger screen

Happy with the hardware, software and design/build, plus I have no problems with it.
I really like the note II, but unfortunately I think the size will be just too big for me (still have yet to see it in "real life")
Essentially will come down to me keeping the S or moving to a nexus device or the RAZR HD (although don't like the look of the front), but I won't be moving to either of those devices until price drops. Guessing they will be £500+ sim free.