IMO option 3 was more about Jakarta EE and MP jointly developing and improving specs of mutual interest for the future Jakarta EE platform.
That is not possible until the MP WG has made a binding decision and all features (or at least those that want to be "pulled" if there was a choice) applied the EFSP first.
There are also other questions on the Jakarta EE side. In the platform project we just covered the topic of namespaces for the schema files. Jakarta EE 9 only envisions XML schema for now, that might change but what if there are one or more extra namespaces then to use like "org.eclipse.microprofile", "mp" or whatever. Should the jakartaee-schemas have to include those schemas defined elsewhere, etc.
You see it's not just a maven coordinate or Java package or semantic versioning.
I put the namespace question on the agenda for the platform project, that is something we can figure out now, and based on that other committees (although the platform project also does votes I think this may have to be done at a slightly higher level) might decide whether one or more additional namespaces are acceptable in the future.