Once Mate is phased out will I be able to install the Brisk Menu on Gnome; XFCE; Budgie or any other DE ? Really love the Brisk Menu.

I believe there are some ideas on porting it to XFCE, but the Whisker Menu is pretty close in terms of functionality, so that's unlikely to happen.

Otherwise no. We have Budgie Menu for Budgie and GNOME is going to keep being GNOME. You'd have to have three different ports for three different desktop environments that use three different APIs and plugin systems. Just no sense in wasting engineering hours in that.

@PublicLewdness "but the Whisker Menu is pretty close in terms of functionality,"

I would say whisker is as close to brisk is gnome-terminal is to xfce-terminal--mostly indistinguishable,
nemo and caja, however, are not even 2nd cousins🙂