Range is the limiting factor here. Even with double the thrust and payload, the Y-20 does not have substantially more range than the H-6K/N. The classical transport airframe simply creates too much drag.
This may or may not be anything significant. AVIC Shaanxi has formed task forces to tackle a new fly-by-wire system and a new flight navigation system. It's not clear if these are related to basic R&D or are specific to a new/evolved design.
