I've made a blog post about it, with some links to for example a FAQ site that explains some of this.
JBoss Enterprise BRMS customers can expect expanded capabilities with a richer user experience and enhanced appeal to business users.
As can also be seen from the presentation you linked, Polymita brings complementary BPM capabilities that will be leveraged and will allow us to bring our BPM offering to the next level. More details, like an updated roadmap etc., will be made available as soon as possible.
Note that the goal is not to replace jBPM (or Polymita for that matter), Polymita enriches the capabilities of jBPM and vice versa, so it will allow us to enhance what we have now and add more sophistication on top.