Oracle Java is based on OpenJDK and certified by Oracle. So I don't see how pouring vast resources into OpenJDK would make "Oracle Java" obsolete.
I don't think that's exactly the case. Oracle Java has some features that OpenJDK doesn't have. What if Google accelerated development of Open JDK beyond what Oracle is brewing so far that at some point Oracle will have a choice of just taking OpenJDK and stamping their brand on it (probably illegal) or being forgotten Java-wise?
I'm not sure Google is really interested in that though.