Alright for what we have figured
>New guys are likely not from our world
>New guys have a city of their own, likely in Ultraspace
>New guys are very pale and use visors, likely to see in the dark
>They warn us about Necrozma in the Altar of the Sunne/Moone
>Lusamine is in threat and Gladion is worried about her possible death
>Pokemon League has been seized by Necrozma
>Necrozma seems to act willingly, not bc muh evil team

My guess is that those ultraguys come from a world where Necrozma consumed all the light and they were left in total darkness, adapting their bodies with those suits to survive, Aether opens the Ultrawormhole looking for the UBs but intead they summon Necrozma who releases the UBs in Alola and likely attacks Aether paradise.
We have to team up with the ultraguys to stop necrozma in their own world, that dark city where necrozma used to live.