That is only true if they are popular. It's hard to believe the Giants and Suns add much to the value of AFL broadcast deals. If they do, it's merely through the crude measure of extra content, which would accrue just the same from a team in Tas and a third in Perth.
You could be right in the sense that NRL viewership might already be at saturation point in NSW and QLD. New viewers might only be available in AFL States and NZ.
The Dolphins will shed light on whether there are more eyeballs within the existing geographic footprint, the sort who only watch Origin or GF, prepared to regularly follow NRL. If they deliver figures similar to the Broncos, will that be at the expense of lower ratings for other clubs? Meaning no increase in overall aggregate.
Analysis of Dolphins TV ratings will inform the decision on where to go to set up a ninth weekly game. Because of the undeniable correlation between playing performance and ratings, one year's data (maybe several years' data) will not suffice.
One question often neglected in debates around the pros and cons of growth is whether the on-field NRL product is currently fit for expansion. Most changes and applications of rules seem designed to increase the frequency and speed with which one bloke smashes into three other blokes. Administrators must think there's an insatiable appetite for bash and crash.
I think supporters, and more to the point prospective supporters, want greater diversity and less predictability.
The way the game is played is largely determined by officials and coaches. Both these groups operate in the grip of various media-induced neuroses. Teams who take risks are often punished. Players who take risks are often derided. Might be an idea to address the effects of all this on the product before placing it more prominently in front of audiences in Perth and Adelaide.