Christopher wasn't here to give an extensive explanation of the meaning of Big Hero 6, so someone had to fill in!It is Big Hero 6. Set Harth is making a joke of when do we get Big Hero's 1-5. And nothing makes comedy funnier than explaining it.
Now, as to why no new Big Hero 6.... yeah, that's a head scratcher. Seems like a money maker....even if a sequel didn't make as much as the original, between that and merchandising, it would be worth it.
There's a gneration of Kids that didn't get into the Baymax hype yet.