I can confirm neither sys-audio or sys-gui is not installed in R4.2.4 by default - as I was writing a new user guide for how to install sys-audio on R4.2.4 (and that started heading towards a full rewrite of all the user documentation, so I’ve not recommenced progressing it further yet).
I’ve loosely seen some information from various sources that make me suspect they will not be a part of R4.3 either. However, I’m not a member of the Qubes OS dev team, so I’m not the ultimate authority on R4.3 goals.
Almost certainly, sys-gui will not be installed by default on R4.3. Probably the same for sys-audio too.
N.B. I’ve seen some forum posts that imply there might be some Salt scripts installed by default. As I’ve never actually read through them, I’m not sure if there is a Salt script that might assist the process.