I'm sure there'll be something icy in specific areas to make it evolve, kind of like how Eevee evolves into Glaceon maybe?? Honestly not sure how they'll work it, or if Vulpix transferred from other games will take on the icy coat (assuming they'll stay the same unless they're Vulpix native to Alola though)
Check small updates thread! It was archived since it was inactive and hard to sustain. We're hoping to do some AMA events in the Main Street (formerly welcome area) at some point though. o/ Celebrations was moved to a subforum of Main Street too.