Hi Luis, The actual segmented area is mostly stable, so even the first version of the atlas has this ~41 million-ish voxels, just they are divided into fewer regions. For example in the early versions there's a very large"Neocortex": https://meshview.apps.hbp.eu/?atlas=WHS_SD_Rat_v2_39um
Then v3 segmented a few (literally, 3 I think) regions from it, related to the auditory areas: https://meshview.apps.hbp.eu/?atlas=WHS_SD_Rat_v3_39um, then v4 got far more detailed, https://meshview.apps.hbp.eu/?atlas=WHS_SD_Rat_v3_39um
The actual downloadable label files show progress, and there's also a changelog in the "Documents" area: https://www.nitrc.org/docman/view.php/1081/191550/

Do you have a concrete VR system/framework in mind? Have you perhaps seen a video, and thought "this is what I want"? I'm still just shooting into the dark, so I can't really suggest what is viable and what is not.

Best regards,
Gergely