Graviman,
Why do you conclude that X2 will operate in autorotation during cruise?
No conclusion. The reason for the preceding post was to invoke technical consideration and speculation. The subject of integrating the rotors, propeller, transmission, motor, and flight controls, in an optimal aerodynamic package, and mechanical package, is challenging.
Stepniewski and Sikorsky present a number of different potential solutions for consideration. On the subject of the rotors being in autorotation during cruise, this additional information has be added to the notes on the
previously referenced web page. It is discussing Sikorsky's earlier XH 59A - Coaxial-ABC.
"In the auxiliary propulsion mode, the ABC rotor power requirements are reduced with increasing airspeed with maximum rotor L/D being achieved at or near autorotation."
"However, with the rotor flying at close to autorotation at high speed, differential collective pitch has little impact on yawing moment ....."
ABC aircraft could be considered as a unification of gyrocopter and helicopter. A similar subject has recently been discussed on a gyrocopter forum, where they were considering the pros and cons of a partially powered rotor.
Any details on how variable Nr is achieved?
CEFOSKEY may be the first PPRuNers to look under the hood (bonnet).
Re Pusher v.s. Tractor propeller aerodynamic:
I think that the Intermeshing-ABC will work better than the Coaxial-ABC when considering the subject of the propeller. This is because the stream-tubes of the Intermeshing rotors are a little more out the sides and away from the streamtube of the propeller.
I've got to be a little carefully using the word 'Intermeshing' since the boss may get mad. 
Dave