I have seen some early implementations of the DAS relying on POJOs persistence (JPA, JDO). Conversely, we could imagine JPA implementation built on top of a DAS. Interesting to see that both approaches have their own benefits.
At Xcalia, our first implementation of the DAS was heavily relying on our POJO persistence mechanisms. We are currenlty working on decoupling these 2 technologies and we now tend to consider both SDO and POJOs are just two kind of consumers, interfaces, APIs of our internal neutral Data Access layers.
Obviously, we will preserve the current bridge between the POJO and SDO worlds: we already publish some detachSDO() / attachSDO() APIs which complement the simple POJO attach() / detach() ones.
Some members of the SDO expert group see SDO as an aspect of POJOs, exactly as JAXB would be another aspect.