I suppose that could make sense - after all, Pokemon is to Nintendo as Frozen is to Disney Princesses - is a part of them (as well as Game Freak/The Pokemon Company), but has the name recognition to be able to stand solo.
Looking at the Nintendo franchises that have sold over 20 million according to
Video Games Sales Wiki:
- Mario (826.38 million)
- Pokémon (480.00 million)
- Wii Series (215.44 million)
- The Legend of Zelda (163.34 million)
- Animal Crossing (78.98 million)
- Super Smash Bros (73.74 million)
- Donkey Kong (65.00 million)*
- Kirby (50.76 million)
- Game & Watch (43.40 million)
- Brain Age (35.51 million)
- Yoshi (29.34 million)
- Splatoon (29.22 million)
- Nintendogs (28.65 million)
- Duck Hunt (28.31 million)
- Luigi's Mansion (23.10 million)
- Wario (22.81 million)
- Metroid (21.45 million)
- Fire Emblem (20.70 million)
There aren't many other franchises that you could build full lands around.
They have already built Mario (1), Donkey Kong (7), Yoshi (11).
You aren't building a land or attraction around Wii (3), Super Smash Bros (6), Game & Watch (9), Brain Age (10), Nintendogs (13) or Duck Hunt (14).
That leaves:
2. Pokémon (480.00 million)
4. The Legend of Zelda (163.34 million)
5. Animal Crossing (78.98 million)
8. Kirby (50.76 million)
12. Splatoon (29.22 million)
15. Luigi's Mansion (23.10 million)
16. Wario (22.81 million)
17. Metroid (21.45 million)
18. Fire Emblem (20.70 million)
In terms of attraction potential:
- If you're building a "sword" land, then you are going to be building Hyrule/Legend of Zelda (4) rather than Fire Emblem (18) if it is Nintendo, Lord of the Rings if not.
- Metroid (17) as a ride could fit in well with a space port land (as mentioned above) - could fit with Star Trek/Men in Black, but wouldn't be any more than a ride. Also for it, and Splatoon (12), apart from a ride similar to Illumination's Villain-Con Minion Blast, I'm not sure what you would do.
- Luigi's Mansion (15) and/or Wario (16) would likely be a part of the current Mushroom Kingdom land, probably as a ride (Luigi) or a Meet n Greet (Wario).
- Kirby (8) could fit in well next to the Mushroom Kingdom, but would likely be a dark ride/merchandise, rather than a land.
- Animal Crossing (5) could probably do well with a specific merchandise location, but would be difficult to build an attraction around (maybe a dark ride around an island/city like Secret Life of Pets at Universal Hollywood, but unless you can show all 488 current villagers, someone's favourite is going to be missed out - I suppose this is similar to Pokemon - 1164 Pokemon - including different forms)
- And then there's Pokemon (2), which we know is coming.
Therefore, if the only other major "land" that you are going to get (apart from Pokemon) is Hyrule/Legend of Zelda, than it could make sense to put it in the same park as Mushroom Kingdom/Donkey Kong Country for marketing purposes. Whether you would put it next to those, or somewhere else in the park (next to Berk?) I don't know. I'm guessing if they were to build it, it would get it's own portal, even if next to Mushroom Kingdom, so they could put it elsewhere.