What happens to OpenJDK when Oracle dies? That's looking increasingly likely on a 3-5yr horizon.
I don't think Oracle will die, but even entertaining the hypothetical I suspect that some other organization (e.g. Apache) would pick up and maintain a fork.
Way too much rides on Java, pretty much every big business has their own customized version of JDK that they support and maintain
The same that happened when Sun died: it gets bought by someone else.
IBM, Red Hat, Microsoft, SAP, Amazon and others all work on the JDK. They would have to step it up to cover the loss of Oracle's contributions, but I am sure they could manage.
Regardless, your timeframe on Oracle's death seems way too soon.
Probably it would get picked up by someone else (e.g. the Linux Foundation)? It's GPLv2-licensed, so it's not like the code is going to be risky for someone to fork