As noted, WWE is reportedly looking to hold one of their biggest events ever in 2018. The MCG (Melbourne Cricket Ground) is looking to host more big events going forward, and WWE wants to capitalize on this desire. The venue has a capacity of over 100,000, and is the 10th largest stadium in the world.
According to the Herald Sun (a major newspaper in Victoria, Australia), WWE has partnered up with Visit Victoria to put on a show in October, one week after the AFL Grand Final, which takes place on September 29. An announcement for the event is excepted to occur at WrestleMania 34 on April 8.
The reports states it would be a PPV event and they would look to bring in names like The Undertaker, Rey Mysterio, and John Cena. If this event does occur, it would crush the previous attendance record (56,214) in Australia, which was UFC 193 featuring Ronda Rousey vs. Holly Holm. Rousey just signed her Raw contract at last Sunday's Elimination Chamber.
It's estimated the event would bring more than $100 million to the state's economy, along with 900 jobs.
Regarding past WWE pay-per-views, WrestleMania 32 in Dallas, TX, broke the 100K threshold at 101,763, although this number has varied in accuracy. Others coming close to 100K were WrestleMania III in Pontiac, Michigan at 93,173 (again, that number is disputed), WrestleMania 29 in East Rutherford, NJ, at 80,676, SummerSlam '92 in London, England at 80,355, and WrestleMania 23 in Detroit, Michigan at 80,103.
Source: Herald Sun