Pixologic is starting to show off some features of its next release, R2 of Zbrush4
So far they are talking about Zee- Best Preview Render EVAR!11 I'm sure if you watch Zee-forums they will have more in the coming days/weeks.
"The BPR renderer in the next version has been updated to a full 32-bits floating-point HDR pipeline. BPR in Z4R2 is capable of rendering high quality
images while utilizing improved materials, lights, and environment mapping."