Why is it an absolute no brainer? They have much bigger IP they haven't used for rides.
Stitch is one of those things that has a subset of very passionate fans, but it's not that huge overall -- it's definitely not comparable to Cars, for example. As an aside, while merchandise sales obviously matter, they don't give a full picture of popularity for a variety of reasons (e.g., just because someone buys a plush doesn't mean an attraction would be a draw, and vice versa). I'm sure Disney has all the metrics they need to accurately measure that, though.
Frozen is much bigger than Stitch, and they shoehorned a bad attraction into a space constructed for another purpose there too... and it's still popular.
I'm not saying I'd be surprised if they built another Stitch attraction, but I don't think it's even remotely close to being a sure thing. If I was betting, I'd probably bet against it (well, maybe other than something like copying the DLP Stitch show as I mentioned above).
All that said, if the live action remake pulls in like a billion at the box office, then I'd probably backtrack on this.