Christian/all,
I have a little bit of insight from the spec committee and although I just have one Individual voice and vote on behalf of the community, I was also the longest serving Individual both in the Java EE EG (since Java EE 6) and JCP EC, part of its duties are now with the spec committee.
We still see a lot of people asking for "J2EE" experience after all those years, it won't die completely even as we approach 2020.
We should try to use the project and spec names where possible. Some like "Jakarta Messaging" still being nicknamed "JMS" probably won't be a big tragedy because if you abbreviate it, you still end up with "JMS". "Jakarta Persistence" also would not be damaged if some still called the API part "JPA", while especially in this case, the Java package already contains the name.
Others like the current "EJB" might be harder because the proposed name would twist it to "JEB" (not that anybody wants to advertise politicians here?;-)
Some specs like CDI always had a terribly long name. There was a suggestion to cut it down to "Jakarta Contexts" but not only would abbreviating that make little sense, it would also diminish the value and scope of CDI by dropping the whole "Dependency Injection" part, while @Inject is what many associate with it although it's only part of another smaller spec embedded underneath.
JAX-RS was always a wrong and ill-fated acronym, the "X" if any could be related to "javax", in reality it was mostly a quick and dirty transfer of the "JAX-WS" (for XML and SOAP) into RESTful Web Services, therefore IMO here it is a house cleaning and nobody should use JAX-RS any more after the Jakarta EE name changes.