Here is the Unite 2016 Keynote presentation which took place in Los Angeles. Octane will be added to UE4.
Goldorak of the OctaneRender Team explains, “UE4 plugin is being released as we always planned, but there are hard limits (as we found out the hard way) by that plugin layer. Unity is going to make changes to their side to enable Octane to seamlessly be part of Unity scene graph, and that will be important for real-time feedback loop, especially beyond 3.x. By way of example, Arnold still supports C4D even though it ships with Maya”, in the OTOY forums. He later adds, “Within the Unity Editor, Octane license activation is planned to be authenticated with your Unity account.”
ORBX will also be built into unity for free.