So far, we have seen Kommo-o and all the Lycanrocs get their own Z-move. And if the first trailer feauturing Mimikyu was anything to come by, it's also very likely going to get a Z-move too.

With all of that out of the way, I also believe that the E4 will have their Pokemon learn these new Z-moves. Hala's hypothetical Kommo-o will learn Clangorous Soulblaze, Olivia's Lycanroc will learn Radial Edge Storm and Acerola's hypothetical Mimikyu will learn whatever its Z-move is called. The only one missing is Kahili, which will probably mean one of the Pokemon she owns (most likely Toucannon) will get its own specific Z-move. But at the same time, Kahili has been shown outside the League in some USUM trailers, which suggest that she might not be part of it in this game.