Sheldon WILL appear in season 3.
It only makes sense, in The Big Bang Theory, it is mentioned that Sheldon recieved his doctorate, at 16, in 1997. Season 2 of Georgie and Mandy’s First Marriage takes place in ‘96, so season 3 will likely head into ‘97.
I have a strong feeling that at some point in the season they will do an episode with Iain Armitage guest starring, because thats a huge achievement and I doubt it’d just be a “Oh shledon got his doctorate!” and move on with the episode.
And I get this show is only focusing on Georgie and Mandy, but storylines have been made for Missy and the rest of the family, why not a one-off with Sheldon? I think the show has established itself enough to where an episode with him could be good.
Or maybe I could be wrong, and the writers forget about this detail.