It would be worth a hell of a lot more than £10m a year.
Not sure. I'm not including naming rights as have presumed that they go to cost of building.
A direct increase on the current £20m from 40k capacity to 50k would take it up to £25m. Sunderland make £5m a year from non-footballing activities (conferences etc) and they have a monopoly on their city. Not sure where other revenue would come from