it depends. I don't know if Element desktop uses it already, but a few months ago I have seen in the matrix live streams that they are already using it for team communication

https://www.youtube.com/channel/UCVFkW-chclhuyYRbmmfwt6w

but it also depends on whether your homeserver operators has set up a working element call/matrixrtc stack for it. if not, the apps will definitely use the old video conferencing implementation