http://auto.howstuffworks.com/dual-c...ansmission.htm
Regor, I doubt anyone here could definitively answer your question, and you have a warranty to consider on a very expensive transmission repair and the possibility the cpu in your car could actually provide the manufacturer with information that would confirm neutral coasting.
My 2008 Altima is the ultimate coasting in neutral and shifting back into gear transmission (CVT-NEVER enigne off). Of course it shares little in common with your dual clutch 6 speed.
If you are willing to experiment with your new car, I would suggest trying shifting to neutral then back into drive at lower speeds, then progressing to higher speeds if you feel comfortable. With throttle by wire and a computer controlled dual clutch 6 speed at, it would seem logical that the transmission would shift into the highest gear when drive is reengaged. This should be confirm able from the tachometer reading.
My Altima seems to shift back into the highest gear, an overall ratio of 2.48 to 1 (including differential) with the torque converter unlocked. This results in a virtually perfect re engagement of the transmission, even at speeds as high as 70 MPH.
I would suspect your car would act in a similar fashion, but that is absolutely pure speculation on my part.
Today I enjoyed a 50 mile stretch of occasional opportunities to coast downhill in neutral, sometimes for .5 mile, then reengaging the transmission to maintain speed or accelerate very slowly. Over 40 MPG in a vehicle that is rated at 31 highway and smooth as silk transitions.
regards
Mech