Considering its predecessor, Super 7, could be used all over the map, I would say no. If it is indeed limited to the stadium, that would be massive wasted potential.
I would say the reason the stadium exists is for players to have a large flat arena, to make arena-style game modes if they so desire. Not because it's the only place where you can create an event.
Imagine being able to create custom races, but only inside the stadium. No using the other amazing, scenic roads in the map. That would be quite the letdown, with little sense.