To me those are two different (although obviously linked by design) aircraft.
3 clues :
- windscreen wippers: size and distance from the nose cone
- main wheels: angle of the fairings relative to the fuselage and ground
- cockpit rear window: different shape (more squarish on the Y-20)
Thought we should stick the two images close enough together to identify any similarities and differences.
What differences can be seen.
- Gear fairing the Y-20 has undercarriage doors outside of the wheels, new aircraft has none. (could be added to Y-20 at a later date), same with the nose wheel.
- Gear fairing is more sloped into the fuselage on Y-20.
- Potential slight differences with nose cone. Blunter nose on new aircraft and less distance from tip of nose to cockpit window
- Hinges on the door appear to be closer together.
- Ratio from nose to wing root looks reasonably close to the same.
- Agree on the wiper changes.
I'm still leaning towards a modification or new variant of the Y-20 against a whole separate aircraft.