Hi Marco,
Since Joram left here, I am not sure who can continue the BPMN2 job. Maybe we could copy some codes from Tom and Joram's new project Activiti, it will implement a native BPMN engine. But at this moment, there are just StartEvent, EndEvent, Task and HumanTask in Activiti, even less than jbpm-bpmn.
Furthermore, the graph used in BPMN is different from jPDL, I think how to design BPMN is another big problem.