I asked Vlado from Chaosgroup if he would disclose a little more about the direction Vray for UE4 will be going. But for the moment it doesn´t seem he want to disclose more than what is seen on the slides. It´s also a very early stage so I respect that. But as a Vray User since the beginning there is one thing I can say for sure. Everything Chaosgroup starts usually turns into a rock solid, really good product.
The slides also mention a potential baking system to replace lightmass in the future. This would be the most important feature to me. Replacing lightmass with a modern renderer.