If those of you who feel that the game is Sydney-centric causes a problem, (I happen to disagree but perhaps it's a case of understanding what "Sydney-centric" means), consider this.
There are really only two States in Australia where rugby league is the most popular football code. NSW has by far the larger population, Sydney is by far a larger city than Brisbane and the game as we know it originated with the Sydney competition. Whilst additional Queensland teams have operated in the past, Brisbane club has resisted spreading the game to a second Brisbane team (hardly Sydney-centric) and the South Queensland Crushers folded years ago. The Gold Coast Titans have had more lives and names than Nellie Melba and continue to struggle. Only the Cowboys really present a persistent, strong presence in the competition. So, how viable, really, is another Queensland team at this stage?
Melbourne have been very successful in their short history and their following is pretty strong within league circles, but their following pales into insignificance compared to the AFL teams. Read any Melbourne newspaper on the weekend during the football season and you will find page after page of AFL reports and hidden away somewhere in the back pages will be brief coverages of the NRL. Even the Storm's coverage is tiny compared to the AFL. Sydney-centric again? Nup. Victorians just don't go for the game like the two other states do.
A second kiwi team? Well, the Warriors are too inconsistent and their track record over the years as Auckland, then NZ, doesn't really support the idea of a second team. Get the first one running consistently first.
Sydney's teams have been reduced over the years and there are now two amalgamations instead of four separate teams, and one team dropped out after an unsuccessful amalgamation. (Norths). That means there are three less Sydney teams now than prior to the NRL forming.
IMO, as long as only Queensland and NSW are the really strong supporters of the game in Australia, and NSW has the larger population (ie viewing audience) and the game is contracted to Channel 9 (Sydney again), there will always be a bias towards a stronger presence, and greater team numbers, from Sydney. And that's hardly the fault of Sydney. It's just the way the individual States prefer their football codes.