Hmm but what is the advantages and disadvantages of a NH-90 configuration vs blackhawk (not comparing the aircraft directly)?
The only significant advantage I see is that an NH90 tricycle wheel style landing gear allows for placement of a rear ramp.
In any case, as Terran Empire said, we can expect any "sinohawk" to be rebuilt with modern technology, engines, avionics, materials, etc. I don't think any of us believe a chinese blackhawk will be a direct copy of the UH-60s the PLA fly in the same vein as the Tu-4 was a bolt for bolt, panel for panel copy of the B-29. Rather, a sinohawk will basically use the prove aerodynamics of the UH-60s they have, but that will be where the similarities end. Basically, the UH-60 is about to be J-11B-ized.
Considering the US will continue operating blackhawk/seahawk variants for years to come, and considering any new multirole utility helicopter is likely still a decade or more away from mass proliferation, I believe it makes sense for the chinese helicopter industry to test their mettle by mass producing a rebuilt version of a known quantity. It allows the PLA to get the new birds they need, it allows the industry to get experience mass producing and also some further experience in the design phase (although experience with Z-10, Z-19 and various Z-9 variants should already have provided much), and sets them up to develop an entirely new generation of helicopters in 10-20 years time, whether it be tilt rotors or push propellers, coaxial, etc.
The recent zhuhai concept models show that studies have probably been made in that direction, and that recent photo of a tiltrotor model in a wind tunnel shows that configuration has also been explored.
A "Z-20" modernized with chinese avionics, powered by a pair of WZ-16 turboshafts (I imagine WZ-9 would not be enough), and if mass produced, would probably be the best way to get a multi role helicopter out to the PLA. Militarizing Z-15 will be difficult and subject to delays, and designing a ground up new helicopter even more so.
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PS, I should point out, that the single model we have of the so called Z-20 seem to show a five bladed main rotor, and the cabin appears to be stretched a little as well... so this bird may turn out to be some kind of "S-70C XL".