IMHO, the target gonna be to get OpenJPA 2.x as part of the OpenEJB. But, i'd like to leave users free to plug any other implementations.
It's definitely the case today (you can use either openjpa, hibernate, eclipse-link).
By the way, to do such, you need
- to repackage the openejb.war if you are using OpenEJB in Tomcat
- to change your Maven dependencies in order to exclude OpenJPA and add your own provider otherwise
The idea is just to extend that by allowing JPA 2.0 as well as JPA 1.0 implementations.