The GPL is just the conditions under which Oracle permits you to use the code. It does not place any obligations on Oracle at all.
The language here seems a bit dangerous. The idea that the GPL is somehow a "viral" license that can steal your code, your rights, and your property away from you is something I thought we were finally getting past. Please, let's not go back there.
If somebody takes the GPL 2+ licensed code and releases it as GPL3 then it is that party that is bound by the patent language in GPL3. Oracle has not somehow released it under GPL3 just because somebody else did.
This is the difference between a license and something like the Microsoft Community Promise. Under the MCP, everybody derives their rights directly from Microsoft. Under the GPL, you get them from whoever gave you the code.
If I download Red Hat Linux, I get all my GPL rights from Red Hat, not from the FSF or Oracle or Linus or anybody else. Red Hat may have gotten the code from them but I got the code from Red Hat.
Unless I completely misunderstand, Oracle could stop releasing the code at all. In that case, anybody that had already received the code could continue to distribute it under any license that is compatible with GPL 2+ (which includes of course GPL3). It would no longer be possible to receive it directly from Oracle though and you could not somehow force them just because they had distributed it previously. If nobody else had a copy of the code it would simply be closed source again.
A license has no impact on the licenser other than restricting what legal action can be taken against licensees who are following the language of the license as originally granted.
GPL 2+ means that Oracle cannot stop you from releasing the code as GPL3. It does not compel Oracle itself to do anything at all.
The relicensing scenario is also possible with the FSF since they require copyright attribution. They could take all their code and simply relicense it under a closed source license if they wanted (however unlikely this is to occur). Of course, any code out in the wild would still be GPL and this would just result in the mother of all forks.