My company is still stuck using CVS because when a new project starts up, they want to use the people who are already locked into the old tech and so they end up going with what people already know. Even teams that started with git have downgraded to CVS once the managers starting looking for ways reuse resources.
I'm not saying all companies will end up doing that, but some certainly will (and already do). They may not be vocal about it, though, because they don't want to piss Oracle.
Enterprise IT is broken enough that those multiple system replacement projects were going to happen anyway because of accumulated technical debt and broken development and maintenance processes, and replacing a backend DB as part of that replacement is a rounding error in expense. Sure, it takes a lot of time for the transition to be complete, but lots of those transitions off Oracle are already underway.
More realistically, it's department politics that are going to prevent any sort of migration.