I'd counter that it's important to specify the time-frame you're talking about. For instance, would you say that they'll try to continue as a big Java user for the next 15 years?
When you stretch out the time-frame, your assertion sounds substantially less credible. At least to me.
Google has an immense amount of Java code, in addition to all the Java programmers it took to write them, a good number of whom are programmers that have written Java for their entire professional careers.
If the bar for getting away from it is rewriting millions of lines of code and retraining 1/3 - 1/2 of their engineers, it seems credible to me.
I'd be very surprised if they replaced all their Java code within 15 years. But even if they do change over, it's still a very good investment for them to continue maintaining and updating Java for the short term.
When you stretch out the time-frame, your assertion sounds substantially less credible. At least to me.