It seems pretty likely we'll get some Alola focus next year, quite possibly at GO Fest, because there is currently no option for a shiny mythical for the 2027 masterwork research. Marshadow is the only Alola mythical in GO right now, but Zeraora is the only Alola mythical whose shiny is released. So one of the following has to happen:
-Shiny Marshadow is released in HOME or PZA/gen 10. This seems unlikely, though: even if Marshadow were added to PZA DLC, the dex completion reward is likely to be one of the Kalos mythicals. If Marshadow ends up being catchable in gen10, HOME compatibility and an associated dex completion reward might be too late for GO tour. I guess shiny Marshadow could just be a random reward of some sort, like a ZA Club reward after they run out of mega stones, or something similar to the shiny Zeraora event when Isle of Armor released.
-Zeraora gets added to GO. Possibly as the 2026 GO fest mythical. Alternatively, I could see Zeraora being a raid mon like Darkrai or Genesect, but then the shiny would probably just be released in raids later, in which case they wouldn't use it as the masterwork shiny. So Zeraora for GO Fest 2026 seems like a likely bet (also possibly for other reasons). especially since it gets a mega that has been officially revealed. I could see mega mewtwo raids alongside the Zeraora research that gives its mega energy, just like Diancie.
-Magearna gets added to GO, possibly as the GO fest mythical. Magearna seems less likely to get shoved in raids than Zeraora. Then, either: the masterwork research actually doesn't give the shiny, but is for original color magearna, or shiny Magearna has to be released in HOME or PZA/gen10. PZA/gen10 release boasts the same problems as it does for Marshadow, but I could see shiny Magearna being a release for full dex completion through the end of gen 9 or pre-DLC gen 10, since OC Magearna was for completion up to Eternatus.
-Alola masterwork reward is something disappointing like Johto masterwork giving Apex shadow Lugia.