To be honest people, it's a bit late in the day to still not have your funding sorted out, far less getting some concrete in the ground, and I think that's how Red Hall will view it.
You're relying on the sale of your ground to fund the building of a Super League standard Stadium. FFS, simple mathmatics state that if you don't get enough from the sale of one, and can't raise the deficit from another source, then your new stadium is never going to get built! Did your BOD give any clues that they were confident of borrowing this extra money or resolving the Xscape objections?
The "extra business" angle is a fallacy. A carpark full of Rugby fans simply means no parking for your own customers......and just how many of the RL fans are going to hang around after the game to spend some time and money? Nowhere near enough to cover your losses I would guess.
And if your new stadium doesn't get built, then your only option to remain in SL is to groundshare somewhere else. And I'd have doubts that you would get a warm welcome from Red Hall for that idea.
Tough times ahead Tigers.