Wow, a lot of ignorant comments here. Anyone who knows about the layout of China, it's population and it's relation to Hong Kong knows that this isn't comparable to HKDL at all.
HKDL didn't have a lot of attendance because there hasn't been much there, luckily that is changing and attendance is increasing gradually. With 3 new lands it will be getting much more attendance.
Besides, Disney would never admit defeat and close a park down, it will never, ever happen.
The idea that Disney shouldn't build in Shanghai because of Hong Kong is almost like saying Disney shouldn't have built in Orlando because of Anaheim...and it's much, much more spread apart culturally than that, they don't even speak the same language in Shanghai (they speak Mandarin there, while in Hong Kong, people speak Cantonese).
I don't believe a lot of Chinese even travel to Tokyo
Disneyland. I read a statistic that over 90% of Tokyo Disneyland's guests are Japanese. Amazing when you consider how small Japan is and the fact that they're constantly showing numbers that rival the WDW parks in attendance.
Now that I've said that, Disney has it's biggest challenge with building a park in Shanghai. Every other park they've built has had a long western influence and is quite familiar with the western fairy tales, etc. I don't believe this is the case with Shanghai.
This means they will probably be making the park a large departure from what we've seen from the other DL parks, if not, I think Disney might be a difficult sell.
HOPEFULLY they've learned finally from the disasters of DCA, HKDL and Disney Studios Paris