I do think another system has a chance of becoming popular but I would guess it would be a large second after DnD with lots of splintering. I LOVE Paizo and Pathfinder. Free online searchable rules are amazing and no one plays 3.5e when pathfinder 1 exists since its just a straight upgrade. That being said both Pathfinder editions are still super crunchy, math heavy and require research to make a playable character. Its still called Mathfinder for a reasons so there is a limit to its userbase.
That being said I know there will be plenty of Plan B and other systems waiting for when DnD really messes up. You can see that with the OGL problems where tons of new content was created especially since you can’t copyright rules or stat blocks. I think the ORC will end up being a longer term stabilizing and creative force for TTRPG. But DnD will still be here because its basically a synonym for TTRPGs at this point.
For sure. I think if some of the big streamers move to their own systems that would have some big blows. I haven’t used Critical Roles new systems but I assume they could get a big switch over if they push it hard