"ToT is safe". If the Cali version is a hit and shows it can bring in extra revenue that could change in short order.
I think it would be difficult to measure if the DCA version is a "hit" or not. ToT was already a popular ride because at its core, it's a fun RIDE. Yes, the story is important and adds to the enjoyment. Maybe I am wrong, but it would have to be some pretty bad theming (like having no story at all) for it NOT to be a popular ride.
I can understand the need to update if something is so outdated. In my opinion, Twilight Zone is classic and can stand the test of time. RnRC, on the other hand IS dated (but still a fun ride) and could definitely use some updates or re-theme.
Still speaking generically, re-theming will of course bring in the crowds, who will buy the new merchandise, because it is new. Therefore, profits & attendance will be up. But whatever decisions are made, they need to be made in the context of a bigger vision.
DCA didn't do this as a one-off, just for a re-theme. They have a bigger plan for Marvel land in that section of the park. So, while it's a difficult pill to swallow for many, the spoonful of sugar is that they know more Marvel is to come.
If WDW were to announce a GotG re-theme, it would REALLY need to be announced within a larger vision of the park or that section of the park.
I think about FEA and Epcot, it seems to be the case that WDW wants to include more IP in the World Showcase. If that is indeed their vision, then - again in my opinion - they should have hinted to that in the announcement for FEA. Even something along the lines of "stay tuned to find out who else you may meet on your journey around the world!" I don't understand why WDW plays so close to the vest. They don't have to announce specifics to reveal a bit of their vision for parks or areas of the parks. Like with this UoE rumor - if they are INTERNALLY still trying to decide what IP to put in, it seems like there isn't a clear vision/theme for what that area of the park should be...but maybe they are still wrestling with even that.