I'll give you my life savings to tell you that when this park is announced, and SNW is featured with the lineup, it'll go viral again. Again, you really are underestimating how the memory of these people work. It'll be successful, very, very successful.
Also, do not by ANY stretch of the imagination, judge the popularity of Pokemon on the popularity of its movies, even a little bit. Period. Pokemon was huge in the US (not just in Japan) long before the first movie debuted here. Its video games, its trading card game, its toys and merchandise, and its movies, continually running animated tv shows (both in Japan and here) and manga--all of it, the whole company, is an absolute juggernaut inside
and outside the industry. Pikachu is immediately recognizable in almost any country in the world--it's not featured in Macys' parade just because it's got some great video games that are really popular with children. Pikachu and even the other Pokemon (especially the original starters) are known to people outside of the world of children/games/anime/tcgs/etc. These Pokemon are almost immediately known, in fact.
It's no secret I'm a huge Nintendo fan. Also no secret that I've been playing Pokemon and following it since the first games debuted here on the Gameboy--my avatar gives away just which Pokemon is my absolute favorite (and my list of favorites is quite long) within the franchise. To give you a small anecdotal story, I have a purse and a wallet that are Pokemon themed--they are actually done in a Tattoo Flash style (which is gorgeous, btw), I also have a small Pikachu key chain attached to one of the handles. I've had this purse for more than a year and I have been stopped (so many times I can't even think to count them) by people of all ages--and again, not just children, or those with children--when they notice the purse, and the characters on it. I've been stopped by women who initially thought it was a floral tattoo flash design who have said, "Oh, wait, it's those game creatures...what's the name...Pokemon? That's the yellow one." (and other variations). I've been stopped by guys who don't play the games, but do play Pokemon Go on their phones. The last time I was stopped was 4 days ago, and the woman was at least 60. She'd never played the games, never watched the shows, didn't say anything about grandchildren playing it (though she could have had them--who knows?), but she still knew it was a Pokemon purse, and she immediately recognized the yellow one, even if she didn't know its name. In my own circles, as well as amongst my friends' and family's kids, I expect this reaction. But it's continually surprised me just how much of the general public recognizes Pokemon, even if they have no idea what any of it is about. And the ones who didn't know Pokemon, or didn't recognize the Pokemon on my purse or whatever? They almost all thought they were cute/adorable/funny, etc. I'm sure some think it's juvenile, but that opinion doesn't affect my experience and I highly doubt having an area featuring Pokemon is going to affect the GP.
Pokemon prints money. In every genre or market they are in, the franchise prints money. And it's not just from children or their spend-y parents. There is an entire market of adult merchandise related to Pokemon aimed at people like me--the games came out when I was 14, some 22 years ago. What Universal has with Nintendo, what it has with Pokemon, is a guaranteed draw, a proven money maker
across numerous generations and genres, and, in Pokemon, 22 years of stories, characters, worlds, games, apps, mythos, and media to draw from. There is no question they will do amazing in a theme park, as both an attraction and a merchandise draw. A Pokemon attraction might not be a typical ride, but it will be a fun, colorful, interactive one. And, again, bright, energetic, engaging, and not gender specific. Also, absolutely
packed. A Pikachu Meet and Greet? There are always lines, even in your regular retail stores. And just like with the princesses, or Marvel characters, or any others, people will wait in those lines for the chance to meet and get a picture with Pikachu (and Ash).
All in all, the movies or even the cartoons/anime, aren't a good indicator of the overall popularity of Pokemon. They are a small part of an absolutely huge brand that just keeps going, in video games, in merchandise, in smartphone apps, in almost every media form out there, really. Nintendo, Game Freaks, and Creatures, Inc (the three companies that own Pokemon) had to create an entire company just for managing the Pokemon brand--and that company has divisions (some huge) in every large market in the world, not just Japan and the US. Not even Mario has that.
TL;DR - Pokemon has zero difficulty translating its popularity from one media to another, even a theme park, because it has been doing it successfully (very successfully) for over 20 years.