I agree with Damo.
The corporate factor is not to be underestimated.
AFL would lose SOOO much $$ if they weren't able to hold it at the 'G.
I don't think they'd give too much of a poo about the average fans not being able to get in, but if they don't have as many corporate boxes and MCC seating to fill they'll never let it leave.
And frankly, there's only MAYBE 2 other stadiums in the country that could hold the GF anyway. So unless every major city's stadium can potentially host it, none should, outside the 'G.