What would Amazon do (Kindle) IF google discontinued Android?

Ok, so as we all know, Amazon forked android for their Kindle tablets. They basically use Google as a free software division of their company. Now, what IF Google discontinued Android for some CRAZY reason, and they did not replace it with another OS. They just dropped out. (Don't worry about that part, it's not the point.) What would Amazon do? Surely they can't just innovate on the UI all the time of a dead os, and an old one! What happens when some competitors have advantages that would mean Amazon would need access to the core OS! (Assuming normally, Google would be doing it already to compete, but Google no longer cares because they killed Android.) What would they do?