Don't mean to be a downer but it's likely nothing.
Geoff was hosting a generic Game Awards meeting with industry folk, Phil was apart of it, some fans were invited to the video call as well to ask Phil questions, Gabe popped in right at the end and answered some questions. It wasn't like Phil, Geoff and Gabe were the only ones there.
Regional Twitter accounts never tweet anything important, with maybe the exception of Xbox UK, if it isn't being teased by the main account it is likely nothing, the New Zealand tease is likely for a NZ launch event (as NZ will be the first place Xbox launches in). Gabe wants to move cause he's been stuck in NZ during this entire pandemic and maybe he's grown to like NZ.
I do think Game Pass will eventually make its way to Steam and who knows, maybe if Gabe decides to retire one day (not really convinced he's at that point yet) Microsoft will acquire Valve but not for a while and I don't think these teases mean anything.
Well he’s 57 right now. Normal age to retire is 65 but I don’t think he will wait that long given his personal wealth. Sometime this upcoming generation we gonna see what he chooses to do upon retirement.