It won't happen again. But if Vince really wanted to, he could pull it off today and draw decent crowds for three big arenas, but definitely not three stadiums. This year WM had 5 headlining matches (Brock/Drew, Taker/AJ, Cena/Wyatt, Orton/Edge, Goldberg/Strowman). If Vince could come up with one more headlining match, and every match on the card takes place in front of the live crowd, that's two headling matches he could have in each city. The roster is big enough between Raw, Smackdown and NXT to fill out the undercard for each arena. If everything lasts 7 and a half hours like this year, that's enough action for each city .
But it will never happen again.