Hi Sasi,
Yes Eric was working on that.. I think that we will be able to answer your question better.
As far as I know you can plug in jBPM5 you identity module, obviously not using the same classes that were used in jBPM3 but using the new ones you should be able to do the same work. If you already have your process defined you should use expressions to resolve your users assignments.
Can you share with us what kind of logic do you have implemented? so we can create an example about how to do it in jBPM5.
Greetings.