The OSR movement was instigated and supported by a very small but dedicated fanbase. This fact remained true until after 5E blew up and lots of people new to the hobby started to explore its fringes and discovered (and some would say co-opted) the OSR.There were enough people still playing older editions to create the OSR movement. That has to stand as some kind of example.
I just don't think people who play D&D would get the same gaming experience, that they obviously love, switching to Call of Cthulhu.
That said I was definitely overstating my case. I think a lot of the people that have discovered D&D recently will be on to other things sooner rather than later, and the collapse of D&D as a published property would both accelerate that and would mostly stop new blood from coming in. How long it would take attrition to essentially "kill" D&D outside of tiny holdout communities is anyone's guess.