Yes,but unless gyms, Pokemon, gimmick and people( which is kinda confirmed) to appear in previous regions, I don't mind that Galar is not main focus. Only thing that's left are locations in Galar.
1. Pokemon in previous regions( confirmed) we have seen Corviknight and Yamper in Kanto.We have seen wild Pidove in Oak's lab meaning Pidove is also native in Kanto, Johto etc. So wild Gen 8 Pokemon will be in other regions.
2.Gyms, IIRC someone said that gyms will be in previous regions unless I am mistaking into thinking that but even if I did: gyms could easily be in other regions under Galar ownership or something.Example Milo to have gym in Johto in new anime exclusive city in Johto.
3.Rivals; Ilima was in Kalos, Paul was in Kanto, Johto
4.Gimmick now this is what I remember is one animator saying that gimmick can appear in other regions. So, Dynamax/Giga will appear in other regions as Max Raid and in gyms since IIRC Dyamax only can be done in that and not in random battle in field.