To speed that up, just buy Postgresql and use that to smother both Oracle DB and to some extent, mysql. Defence only helps that much, offence can do it a lot faster on their own DB territory.
Better yet, buy EnterpriseDB that's actively targeting Oracle's market. Put a bunch of money into expanding it with conversion tools from Oracle to not Oracle API's it will use.
Given how much Google owed Sun in terms of technology and employees pulled from Sun over the years, I always thought not buying the company was an especially cynical move. Sort of like, "Ha! We got all their stuff for free and now they're gone! We win!" Payback's a bitch - though in this case it's not just going to be Google that pays. Oracle is vicious.
Let's give Oracle 10 years from now to fade from relevance as yet another fucked by cloud vendor and Google can then orchestrate a hostile takeover.