Yes, we're still using Unreal Engine 3. When we started on this project, UE4 was announced but not available, plus by building off the base framework already created for RO2, it has let us spend more time iterating on the gameplay side of things and less on building a new framework from the ground up, which is particularly important for us as this is the first time the RO franchise has stepped outside the comfort of WW2 into an era of automatic weapons and more modern technology. i.e. We get to spend more time making sure that the Vietnam theatre works in an RO context without breaking the gameplay, and less time on things like building a scoreboard, again. Plus, it means we can finish the game about 2-3 years sooner than we otherwise would.
As far as porting is concerned, no, we won't. It's by no means a simple thing to port between engines, as UE4 differs significantly.