I have messaged them but I doubt I will receive any answer. I know from the past that they are not very communicative. There are some users in the flightsim community that have better relations with them I believe, so I hope this catches their attention and maybe they know more.
EDIT: Received a very pleasant answer from them. Really did not expect that, especially within a day. Here is what they wrote:
Hello
The MSFS version of VoxATC is at an advanced stage of development and should be available in the next few months.
Thanks for your continued interest in VoxATC.
Regards
VoxATC Support