I don't think they should make another compilation game because they already did a tremendous job on one. I think that they could maybe add in a set of microgames returning from other games in the series, but I would not want another compilation.
With the Switch 2, it has been heavily rumored (and hinted) that there is an inside sensor that contains a way to play the Switch with the Joy-Con on its side so you can use it like a computer mouse, which could make playing certain games a lot easier. As a result, I definitely think that a new WarioWare could take inspiration from Gold's "Mash!" "Twist!" "Touch!" "Blow!" commands. There are plenty of fangames that have used a mouse and proved that the gimmick can work for a WarioWare game, so they could do something similar. Have one (or two) Joy-Cons on their side and use them as a pointer, or you can twist and shake them to emulate Twisted!'s controls in a new format. Or you can combine this with using other motion controls like in Move It!, the IR Camera again (if the Switch 2 has it), and button controls. But I am sure they will think of something, they haven't run out of ideas yet. I do not think I would want another Get It Together! either as they already did this idea well enough.
Next best thing would be a sequel to D. I. Y. but you could potentially use these controls instead of just tapping the screen, and there could be an updated interface. But I would really want a mainline game and Wario Land game more than anything else. I do not think another WarioWare game would happen for a while considering that we just got 3 in the span of 5 years, and I am hoping that the team could now focus their efforts on Rhythm Heaven instead.