Reposting this since it was like one of the last posts and I got annoyed by everyone switching to Doomed after Emily's tweet:
BotW2 would be one of the most heavily protected IP's and teams there.
I highly doubt many insiders' sources (even if they're Nintendo employees) would have access to anything going on with that team outside of internal rumors and ballparks. Maybe BoTW2 is on track for 2020, maybe not, but I doubt that Emily or anyone else would necessarily know at this point.
BoTW2 - whether meant to be the big Holiday game or not - will be one of the biggest flagship games of the Switch's life. They're gonna want to play their cards as close to the chest as humanly possible there.
If an insider wants to prove me wrong tho I'm happy to take it