The NRL could easily expand to 18 teams by 2022 then 20 teams by 2025 which would usher in the 2 conference format.
2030 at the earliest for 12 teams in each conference.
Sure the NRL could support 4 more teams over the next decade or so, but you are totally off your f**king head if you think the NRL could support 7 expansion clubs in ten years.
You'd totally tank the standards of the competition (and probably the ESL as well) as the growth in the talent pool through traditional means (i.e. developing juniors) definitely wouldn't be able to keep up with the pressure of adding 210 full time professional players over ten years.
If anything went wrong with any of the clubs the NRL wouldn't have the means to prop more than a few up at any one time, which would make it an incredibly risky proposition because if they started to fall over (and it's inevitable that some would struggle financially) then there'd be nobody to catch them as they fall, and you'd risk a repeat of the domino effect we were starting to see in the 90s when the NSWRL grew too big too fast without rationalising the competition first.
On top of all that, at the same time you'd be pushing this massive expansion drive the value of broadcasting rights are almost certainly going to start to drop, which will add an extra layer of risk because of the uncertainty of whether smaller sports leagues, such as the NRL, are going be able to attract similar value contracts through other means, namely streaming.
And because of the geographical spread of the clubs there's no way to do a balanced, and more importantly fair, conference system. You'd inevitably create a system that vastly favours one conference over the others (probably the one with the most Sydney clubs in it), so unless you are willing to accept that sacrifice, which I'm most certainly not, the whole idea is a total non-starter.
Basically, unless you rationalise Sydney in the process of this huge expansion push it's simply feasible to expand by that many clubs that quickly, and the chances of Sydney being rationalised arr slim to none!