Obviously a key difference there is that in the 60's it would've been a lot easier to get people to support a new team in their area than now when we've got an established competition that is all through Australian media.
Back in the 60's the competition already got reasonable media coverage and was established throughout NSW, and considering that the expansion was in Sydney I'd say that in real terms there's really no difference.
Outside of that though, my point was more to do with the TV ratings aspect. Will it actually impact ratings at all given the same people who already make up the Brisbane NRL audience are the one's who will be watching? Adelaide has grown to about 80,000 households watching Origin and the Grand Final while Perth is onboard for close to 100,000, those are areas that would see a much large uptake in terms of weekly viewership with a team. Alas, I think that Adelaide will need to wait a long time which is a shame as they punch well above their weight in terms of sports attendance and viewership per capita.
Of course it would, it'd give the Brisbane audience another game that directly appeals to their market, which will give the broadcasters another game that rates well (probably in numbers similar, but slightly lower than, the Broncos) which they can sell advertising on.
In other words, instead of having one match that rates well in Brisbane, the NRL and broadcasters would have two, and they'd be engaging a larger portion of the Brisbane market, which is incredibly valuable to both the NRL and the broadcasters.
That is more or less the whole point of a second club in Brisbane, not to create new fans per se, but to get more RL fans in Brisbane to actively engage in the product, and to make a shedload of money in the process.