My biggest problem with "Donkey Kong is a definite for Orlando" is where is it in the video? All three sides of that U-shaped land are Super Mario related. Donkey Kong is jungle-themed, which is seen all over the treehouse concept art. That art and the official video do not match up.
I've done the logistics and the USJ parking lot where they are building this fits almost perfectly into the KidZone area. It's actually kind of scary because the diagonal border it shares with Hogsmeade matches almost perfectly with the ET building. Which is great for Universal, but it doesn't leave room for that treehouse and a coaster.
Some of the rumors say Japan is only getting TWO rides. I think that has to be right because that parking lot is NOT huge. Being generous, it's about 200,000 square feet. The Gringotts ride building is about 85,000sf. The Mummy - minus the facade - is about 65,000sf. ET is about 56,000sf. Even smaller rides like Spider-Man take up about 50,000sf. (I didn't measure Forbidden Journey because I'm not really sure what's ride building and what's other stuff.) Three smallish ride buildings would take up 75% of the land here, and that doesn't include all the facades or the restaurants or the restrooms or the shops. (They're probably going to build something similar to Fast Food Blvd between the two ride buildings and the one in Florida takes up around 20,000sf of space. The two-story one in Hollywood takes up less space, but it's hard to know how much less as it shares kitchen space with Hogsmeade. It's somewhere close to 15,000sf.)
Seeing the concept art for MK, I'm thinking speed isn't going to be a major factor for the ride, so it probably can sit on 50,000sf or so. (If you pause the concept art video right before it ends, you can see the diagonal Hogsmeade border. In the original concept art, they made this look like a bridge and it shows people going under it, like it was leading elsewhere. It's probably just going to be the main gift shop for the area, something that isn't exciting to show in concept art. If so, that means the Mario Kart ride building can be about 275 feet long, which takes it to that diagonal. At 175-feet-wide, we're right about at that 50K mark. And it can't really go too much wider than that because the whole area is only about 425 feet at its widest. That courtyard has to be around 100 feet wide if they're going to plop an island down into the middle of it.) I suppose they can build two rides on top of each other in the other ride building, but I don't think they will. That's just too expensive, and the rides that would fit in those spaces would be C-Tickets, at best. So that's two rides for Japan, unless they throw a flat ride onto that island.
Even though that plot of land plops down perfectly into USF, it doesn't mean they can't expand it easily. If they remove the Animal Actors show (Why haven't they moved this thing over to IOA's usually-empty theater?), then they can build the Donkey Kong miniland here. An alternative would be to move the U-shaped area back towards the empty area on the other side of The Simpsons Ride a little, which would open up the area that already has a coaster and a play area (Is there a reason the art coincidentally shows both of these?). This, of course, blows my Nintendo Store out of the water, as it would then become an actual bridge, but it could easily be moved to be the berm between DK Country and the ET esplanade. (Having a Donkey Kong miniland makes the plan work for USH as well. The area behind Transformers - an oddly-placed plot of land - could easily become the DK Country miniland.)
Personally, if the coaster isn't spectacular, I wish they'd just make Kirby host the kiddie area and plop Donkey Kong into Toon Lagoon. The flume needs some desperate theme work on it. And the rapids ride would be great with the rafts themed to barrels. But I think we're going to get Dreamworks overlays instead...