Is there any rumor at all that might point to Supercharged being replacement by GB? I thought the only crumb we had was BTTF replacing Supercharged but that was just a slim chance (someone said someone else said this on another forum, so could be a game of telephone at this point).
Correct me if I'm wrong, but the three options right now for the GB IP are: 1) meet and greet at Firehouse, or 2) nothing, or 3) coaster RRR replacement. The only 'proof' for 3 is the sign on the work walls and proximity of the project, everything else might point to 1 or 2. And I don't think we have any suggestion that anything else for GB could be coming to the parks.
But yeah, I don't see why they couldn't have three projects over the course of 5-6 years. They've done it before at USF. Remember they added Springfield (2013) at the same time as Diagon was under construction (2014), and that's was shortly after Despicable Me (2012). (Note Springfield was just the 'land,' the ride opened years earlier.) And Fallon and Supercharged were announced in 2015, which opened in 2017 and 2018. So within roughly 6 years, USF added Despicable Me, Springfield, Diagon, Fallon, and Supercharged, at the same time they were building attractions at IOA, building VB, significantly changing CityWalk, and finalizing plans for Epic. Say what you will about the quality of these USF attractions, this was a significant amount of resources poured into USF. No reason why Universal can't do this again.