Hi Jan,
Currently there are no plans to provide support for Java EE 7 in SAP NetWeaver AS Java. A good read on this topic is the Karl Kessler article in SAP Insider for the 7.5 release. There is also a lengthy discussion in When will SAP Java AS for EE 6 see the light?
Although a full support for Java EE 7 is not planned, we are currently working on a feature that will allow you to plugin a third-party or open source implementation of JPA (like EclipseLink). Although this was possible in the past, it was not possible to use the new JPA 2.0 features.
Best regards,
Nikolay