They're not in the same league as NRL and AFL.
Agreed. The FFA seem to be finally conceding this, with the rumours of Lowy spouting an October-March season with 10 teams, 7 on the eastern seaboard.
As for Union, they're trying to turn Super 15 into their national domestic comp - but with only 4 teams on the Eastern Seaboard compared to the NRL's current 15 and the AFL's future 14, it would be a big call for anyone to suggest that they'll overtake either one any time soon. The calls against professionalism in Argentina's rural unions seems that having 5 teams in Buenos Aires is unlikely - so Argentina would likely just play in a 4 nations tournament only - and Pacific Islands is a long shot.
There's talk of expanding it to 8 teams per country - you'd have Adelaide - but then what? You'd either have to cut into Sydney/Brisbane's support base or set up in a regional area. It kind of defeats the idea of the state unions. Under that structure they'd have 14 meaningful games a year - and 8 others against NZ & SA that would start to pale into irrelevancy. It would also impact negatively on the Sydney & Brisbane comps if 2 of the new 3 were in NSW/QLD. Plus it would also affect the ITM & Currie cups if it ran for 22 weeks.
I'm not sure what the long term plan for Union in Australia is. But having a rag tag bunch of comps - Super 15, Shute Shield, Rugby 7's, Four Nations, ARC etc in dribs and drabs and eating into one another is not the answer.
As for the long term expansion in NRL over the next 25+ years, it likely needs:
* QLD - 2-3 new sides, guaranteed two to three game a week there, with 2 QLD teams featured on FTA coverage every week, and a local derby once a month at least
* NSW - admit the CC team and retake North Sydney
* VIC - carve out a bigger market share in Melbourne - make the Storm every Victorian's first or second team
* WA - admit the Reds - make them every Western Australian's first or second team
* NZ - admit 1-2 sides - preferrably locking up the remaining 2 large populations centres - guaranteeing a NZ game every week and local derbies once a month
* PNG - admit the Port Moresby side
* SA - would likely be the last domino
In the long run you might see:
NRL - 22 to 24 team comp - 18 on the East Coast
AFL - 18 to 22 team comp - 15 on the East Coast
Union - 18 to 21 team comp - 4-5 on the East Coast