The JDK would promptly be forked from the last-covered commit, presumably by a coalition of Amazon, Azul, IBM, Red Hat, SAP, Google, Microsoft (amazing times we live in) and Pivotal amongst others.

What enterprise customers want is certainty. Given the choice between "Java by Oracle" and "Basically still Java by Literally Every Other Enterprise Software Vendor", they will pick the latter in a heartbeat.

It would be chaotic and disruptive, but once the dust settled Oracle would (again) be holding the fizzle instead of the bang. That's how we got Jenkins out of Hudson, which has an unrivalled penetration of enterprise.

Disclosure: I work for Pivotal, we sponsor Spring and have a deep interest in the evolution of the OpenJDK. This is of course personal speculation.