Relyon,
That Bugatti looks well thought out. Very low frontal area and as simple a profile change as possible to minimise velocity hot spots. I'm slightly suprised that supine position didn't catch on more in powered fixed wings. The risk with a drive shaft is torsional resonance, particularly with direct drive. With a gearbox the inertia of the propellor is reduced on the shaft (proprtional to ratio^2), shifting the frequencies up (proportional to ratio). That said i imagine this would only be a concern when the prop was at low thrust pitch, since there would be damping at high thrust pitch.
riff_raff,
That is the million dollar question - actually the market will likely be billions.
I'm not wanting to upset our tilt-rotor friends here, but for me it all comes down to lowest disk loading and smallest landing area planform. I notice that this new concept reduces from full tilt to just enough tilt to achieve cruise. That goes a long way towards answering the concerns about autorotation from transition, particularly if the tilt mechanism is passive using rotor to vector tilt (would need a damper rather than an actuator). I would imagine that the wings make up for the retreating blade loss of lift, so basically a laterally seperated ABC. Looks like the influence of one particular highly regarded engineer and TP.
My own view is that the market will be big enough for both concepts to have a share. That said X2 ABC is a purist concept. The engineers started from a machine designed to hover and scratched their collective heads to figure how to make it go faster. A wing is always going make life awkward for the hover: they want to take up room and will always stall as speed reduces. To my way of thinking a rotor capable of reacting low rpm lift at high speed will be lighter.
Time will tell...