When can we expect China to become a developed country? China has the 2nd largest GDP in the world and also has a high GDP growth rate. According to Richard Lynn's IQ and Global Inequality, the Chinese have a mean IQ of 105, which is one of the highest in the world. So, it just seems to be a matter of time before China becomes a developed country. The only question is when: Will it be 10 years from now? 20 years? 50 years?
Just because a country has a lot of resources (including human capital), it does not necessarily form a path for a developed nation. China is also very involved in military conflicts. It just takes one war for a country to drift back decades. Also, you can't ignore the brain drain problem. 

With that, "developed" nation is a fluid definition. What does that mean? Is the US developed? Thousands of US citizens don't have electricity yet. No clean water. Massive health care and student loan crisis. Not to forget the trillions of dollars of debt. But many would consider the US a developed nation. If you are basing "developed" as in militarily-wise, then China will soon be a developed nation, if not already.

However, if you account for freedom of speech and all, then China is still decades behind from its neighbors like India.

Hope that helps!