Phase 4 in the North Atlantic is due to go live in a few weeks. Delays in implentation are not always due to technology, but often due to the time it takes getting all the service providers, operators and ICAO reps in a particular region to agree on an overall standard to be introduced re. message sets, NDA transfers, etc.
Perhaps the Chinese, having the luxury of a huge area under their sole responsibility, have been able to speed up their implementation. Countries with smaller FIRs and reduced transit times may have additional issues with successful log-ons to Current Data Authority and Next Data Authority transfers to/from receiving sectors whose systems may not be in place or so be well advanced, etc.
Just guessing mind'ya, but it is a complex area, not just in terms of technology.