Lets see whats most important ... some of them are already planned, i know
-Focus feature: draw a region and focus all gpu power on that area only, godspeed

!!!
Materials:
-(Hopefully) Fully featured material system, since it is the first step to be able to do the full range of phenomena on surfaces.
- day light for outdoor and portals for indoor, as well material based light.
-That includes different node types to work with(divide, multiply, ramp, etc...) , and more options to be able to tweak (fresnel factor, BRDF, absorption thickness, anisotropy, SSS, Dispersion, IoR values below 1, Luminosity,..), multiple shader layer...
-save those as custom settings or library
Camera:
- a realistic camera lens, including bokeh, dispersion and distortion. I even would love to see the possibility to be able to add a bumpmap or procedural scratch or dust approach on the lens itself.. that would be cool !
Output:
-Different render passes and formats like .hdr, .exr, spherical or longitude based panos, or maybe some baking to texture function.
-The feature to save the progress of the rendering, so you can continue later to render even further... if possible.
Scene:
- Node based scene assembling of multiple obj's and other components, custom groups/parent/child relationships.
That already is a lot but for the distant future:
- Animation starting with camera and lights as well as material attributes, later on complete character, baked/cached scenes ? Could be a memory hog

- Plugin based connection to other packages like Maya, Max, Modo, Softimage or many others..
- atmospheric phenomena, like fog and haze / volumetric procedurals... maybe someday even crazy volumetric voxel stuff like fumefx XD > this will require a few years until cards can munch those memory monster easily i guess..
Some improvements:
-A visible grid .. i know there is the button so its close.
-Axis indication and grid units per screen space (so you know the scene scale)
-Key to move and focus on object/scene, so camera will spin around that locations center, could also be picked manually (like in Zbrush local mode)
-Show nodes in collapsed mode first, way more overview !!!
-Currently node inspector is a little hard to view in the first moment, with the way it shows the values. I think this will become more artist friendly/ less programmer style by the time

-Prevent render viewport refresh by simply moving a node
-a small info picker for color and values of the framebuffer, maybe a histogram would be nice as well.
And finally
Eastereggs, cause every cool programm got those 