Interesting to look at the Titans from a similar perspective. I grew up on the Tweed, which the Titans claim as part of their catchment, as did the Giant Seagull Gladiator Chargers. The old team had next to no local support, but there were plenty of Saints, Tigers, Eels, Dogs, Bunnies, etc. supporters (and still are). One would have looked at that and concluded that the "locals won't switch from their old team to support the local team" argument holds water. Such a conclusion misses one crucial fact: the Seagulls were useless at promoting themselves and seeking to engage the local community, and with this added to their worse-than-Souffs on-field performances, it is little wonder almost no-one supported them.
The Titans, from day 1 (long before they played a game), have been a different kettle of fish altogether. They have promoted themselves long and hard, especially to the local kiddies, and they actually do a decent job of engaging the Gold Coast and Tweed communities (e.g. the Titans name, colours, and uniform were all voted by fans). This coupled with the fact they've been competitive on the field since day 1 has built a solid local fan base (it still makes me smile every time I see someone wearing a bit of Titans merchandise, because I remember well how rarely I ever saw anyone wearing Seagulls/Chargers gear).
So I guess the point is that if the job of promotion is done properly, the local community will embrace a new team. And this includes people like myself and Timmah, who will follow the local team as a second team.