The Rathalos arguments are pretty interesting. I'm still very confident about Skull Kid's inclusion in big part because the Moon AT. In my mind, it counters almost every other possibilities:
Not in the game at all: Why not put Skull Kid with the Moon as an AT then?
It would be the most logical choice.
He'll come back as an AT: And his signature move is a separate AT?
Makes no sense to me to have them both as 2 different ATs.
He'll be a boss: Sakurai and his team must be aware of the support behind him and the effect of the Moon AT's reveal on the fanbase (combined with the absence of Skull Kid), i'm not sure they'd tease and troll
that much on purpose.
I may be wrong but that's my reasoning for the moment. Logic as you say
Plus those 2 chairs are still looking at me from afar, laughing