Are you going to include at least limited wave tracing for [FONT=lucida sans unicode]reverbration (à la A3D back in its day) in the next versions of UE4? And also physically-based per-material or per-physical material reflection, absorption, etc. properties? I think it would be really great for the engine to be able to do that, and also very helpful in games such as Unreal Tournament in the gameplay, for locating enemies and the like, not just for immersion alone.
In addition, now that Windows 8 supports hardware-accelerated audio again, I think it would be awesome to include support for it in the engine. Would probably help you get some more cash for supporting some sound card and hardware manufacturers, in addition to making a whole lotta audiophiles happy.
The future of the audio engine is explained here : Audio roadmap and APIs - Feedback & Requests - Epic Developer Community Forums
So any advancement regarding audio dsp, including various reverb technologies, will be up to third party engines like wwise and fmod - both will most likely release something in 2014.