What figures do you have exactly that suggest Lost Continent is "the least popular land in the park"? Are Mythos sales down? Is Sinbad not filling up seats? Is Poseidon's Fury not attracting people?
I think that when you compare a land with no rides to a land with two low-capacity water rides such as Toon Lagoon, you're not going to get a fair evaluation of how popular each one is. Now, you may have some hard facts that I don't have but the way I see it, Toon Lagoon and Lost Continent are incomparable...if you're judging popularity by queue times, you can't because Ripsaw Falls and Popeye are low-capacity rides. If you're judging popularity by food sales, you're discounting Mythos, one of the best theme park restaurants in the world. If you're judging by merchandise sales, you have to look at the success of Lost Continent's rather successful specialty shops that Toon Lagoon has no comparison to. And if you're judging it by level of theming then Lost Continent would win by a landslide.
Regardless, I hate the idea of Willy Wonka in IOA--something about it just rubs me the wrong way. It's just one story, I feel like there isn't enough substance to draw from for an entire land (yes, Jurassic Park, although dinosaurs are a lot broader and more popular than a theme like candy). The movies are just creepy to me. Also, something I've noticed, the Wonka candy company sells mostly fruity candy rather than chocolate (Bottle Caps, Shockers, etc) so would Universal have to create another line of Wonka candy just to fit in theme?