In Guangzhou, at the Chime Long Amusment Park complex, they have Safari World, that actually has a very large panda natural habitat. It's next to the koala habitat. But no, I haven't seen any exclusively Panda themed parks.

As far as why that isn't available, I'm not real sure. If it was located in a larger city like Shanghai, Bei Jing or Hong Kong, it might go over well becasue tourists might patronize it, but as far as local people, I don't know if they are as crazy about pandas as those from other places. Personally, regular pandas are cool, but kung-fu pandas are better!

There are Giant Panda Research Bases in Chengdu, Bifengxia and Wolong (although that one is closed because of the earthquake in 2008, due to reopen this year). You can visit with the pandas, see them in semi-natural habitats, and even have your picture taken with one. 

Look up Chengdu, it's like panda land

There's a panda breeding center in Chengdu that people go crazy over. I've seen some photos where people actually get to hold the babies. 

I think that since the panda is a native animal, it's not as cool to locals as it is to foreigners. I also think that most visitors to the park would be Chinese, so theme parks are based on what Chinese people find interesting. If they thought pandas were the best thing ever, of course they'd have more amusement parks related to the animal.