I think the Broncos will be the name chosen. As jaybs said, Broncs were pulling 5k in SL1 and SL2, but that was with proper investment, and proper marketing, also a Challenge Cup Final might have added something to the mix
But I think Broncos, with the Yellow, Red and Blue shirts encompasses the identity of London Rugby League. Mix that with a new marketing strategy over 10, 15 years, and we'll see a booming London RL scene at the end I think.