China really doesn't have any land-border threats, even the threat of land war in Korean peninsula has significantly reduced. Is that really wise to invest in a new platform? Then again, it can be argued it's neccessary given Russian developing the new T-14 Armata, so I guess China should develop one to keep pace, albeit at slower rate.
Why do the Japanese have a first-class MBT? However powerful your navy and/or air force may be, you'll always need boots on the ground to control territory. And infantry are awfully vulnerable to armor in many parts of the world and even in an urban environment a tank has its disadvantages.