I've been doing some DA40 and DA42 delivery flights recently from the Diamond factory, so have been keeping an eye on progress on the DA50 for a few months. At the moment, DA50 is Diamond's third priority after certification of the D-Jet and the new engine. Test flying of the DA50 protoype has also been very limited by the weather at LOAN as VFR is not possible there for long periods due to fog. I don't think DIamond have even established a schedule for DA50 certification and delivery, but I don't expect it to be soon. The DA50 really is remarkably large - I would guess bigger than a Cirrus so I am not sure that a 170bhp engine will really be enough. It looks more like it is built to take a small turbine up front!
For those slagging off Diamond build quality I can assure you that it has improved very considerably of late (and I don't think it was that bad to start with). They have built two new hangars which are dedicated to finishing and quality-controlling the planes before delivery, and each plane is checked very meticulously. I have never found a single build fault in any of the planes that I have picked up from the factory. The only exception to that is that they never seem to tighten the elevator control commands sufficiently at the factory leading to mild oscillation when climbing on the autopilot - but that is a five minute problem for a technician to rectify.
They are super aeroplanes, and very comfortable even on long flights. With long-range tanks options both DA40 and DA42 have 7.5 hours range and they are adequately comfortable for the pilot even on flights of that length (and I know other delivery pilots who have done far longer flights with a supplementary tank on the back seats).