If the design process started 20 years ago and the production orders were placed 15 years ago, then it is not unreasonable to expect the next generation of tank to be in the pipeline now. This is especially true for a rapidly developing country.
Now, I dont know if the operation of modern tanks, differs fundamentaly from the operation of older ones, or whether an Abrams functions pretty much the same way as say a Tiger or a Matilda.( I dare say you do and can advise). If the difference is great, how well would the PLA of 15 years ago have been able to operate equipment that corresponded to Western Levels?
Irrespective, Chinese production capabilities have transformed themselves, largely out of recognition, in this period which means that 15 years ago "a modern" MBT would probably have been outside of their cost-effective production capability, whilst today this is no longer likely to be the case.
China now, probably faces the same problem as all Western Militaries, which is that the rate of increase of civilian technology, is so much faster than the speed of the military procurement process, that actually pinning down a set of working specifications is becoming increasingly difficult.