I found the source of the "five unannounced games" tidbit, but it turns out that it might be more. It comes from a very reputable insider on Resetera.
The quote:
"Indeed. Five is the floor (minimum) -- not the ceiling. The ceiling could be as high as 11 or 12.
It's difficult to give an exact number because any game can be pushed back to 2020 for marketing/scheduling reasons.
Let me try to explain this better.
The "Most likely" Nintendo-published game announcements for 2019. (70% chance or higher)
1. Mystery game #1
2. Mystery game #2
3. Mystery game #3
4. Mystery game #4
5. eShop game #1
6. Mystery Wii U port #1 (2013 title)
7. eShop game #2
8. New Labo Kit
The "Maybe" games for 2019. (The wild card titles - 50% chance or less)
9. Retro Studios secret game (this is assuming it wasn't canned)
10. Metroid Prime Trilogy (assuming Zell's info and Imran's info are correct)
11. Mystery Wii U port #2"
She hinted at one of the unannounced games being something from Platinum. And the mystery games do not include Retro or MPT. So that's interesting. And the 2013 Wii U port could be any of the following: Super Mario 3D World, Pikmin 3, WindWaker HD, Wonderful 101.
Take it with a grain of salt, but this could be amazing if true.
Edit: Just to give a more pessimistic sort of view, she could easily make this all up and still be correct. The next Wii U port is almost certainly a 2013 title, as 2013 currently has the best available games. It was clear that, even before Nintendo started teasing the unannounced games, we'd end up getting more games this year. Four games is a good number. And the E-Shop titles do make sense.