I can't. Lip isn't that hype of a character. I can see them saving her for second-to-last, but not last. Last IMO is going to be someone big. I'm honestly predicting Banjo now.
Lip... is still in a weird position. I'm predicting AT for right now. Her flowers getting redesigned is still weird. I don't understand why that happened at all. Maybe there's a chance of a stage and slim chance of playable.
Because Mute City Melee probably is in, they just haven't announced it yet.
I think Sakurai's statement in the Direct was a mistranslation. He was saying we're now "up to 103" stages, rather than "our max total is 103". We're also missing Orbital Gate Assault, but there's a planet on Meta Knight's page that is only found on Orbital Gate Assault. Plus, I find it hard to believe he'd reveal EVERY SINGLE stage six months out, and not have a single other new IP.
Ok, its not Meta Knight's page, its the About page, Meta Knight is just in the image.
https://imgur.com/gallery/QHuJEcK
Another possibility is that it could be a new Star Fox stage (based on Zero) with that planet in the background instead. Either way, we're not done with stages yet.
EDIT: Just wanted to point something out I noticed.
They're still hesitant to reveal Lip's Stick fully. This... could be something of note. Lip could still be a surprise character, maybe. For some reason, Lip's Stick isn't listed on the items page, despite being on Richter's page. Its really weird. I don't quite get it. It'll be interesting to see how things play out here.