It wouldn’t make sense to have three teams on SEQ and only two in Perth.I don't think Brisbane2 is a legitimate option that's being considered right now. I was more so commenting on my belief that what's best for footy in Queensland is to eventually get to a point where we have AFL games being played in the Brisbane market every week, just like every other major capital city in Australia currently has. Population growth shows Queensland is only going to become more appealing as we go forward and it would also reduce the travel factor for the QLD teams to give them a better chance of being competitive long-term. You need competitive teams within a market to grow the game e.g. look at the growth in attendance/memberships in Brisbane since the Lions have been legitimate flag contenders over the last 5-6 years. Plus, we can't just solely rely on the Lions forever - they will eventually drop off. Having a second team to cover that drop off period should minimise the risk of what we saw between 2010-2018.
At this point I doubt the 20th team will be based in Brisbane, but that will really come down to when they make a decision on it. The AFL doesn't seem overly keen to start two new teams at the same time from what I can see. Perhaps they learned their lesson from the GC-GWS experience. So the next bout of expansion might occur around 2032ish? By then the Olympic infrastructure will be built and there should be a brand new stadium in Brisbane. So perhaps the Queensland government will be more motivated to have new facilities used and weekly AFL games taking place at the new stadium.
I also doubt we'll get to a point where a Melbourne-based team are legitimately considering relocation in the next 10-15 years. I can't see any of them allowing another Fitzroy situation to occur. So if the options for a 20th franchise are Canberra, Darwin & Brisbane2 and they would enter the league around 2032 then I think Brisbane would be a good chance to win that race. Perth3 could throw a spanner in the works, though.
If they want more games in the new stadium from 2033, the logical step is for the Suns to play two games there, rather than in Darwin.