That's an interesting question, and something I had wondered myself.
Apparently...other than the problems with thickness of the discs and them not playing in certain players (which may put people off), there have been problems with DualDisc getting into the UK market because DVD+ discs have their foot in the door over here (the Kasabian album was released on that format in limited numbers).
I think it would be safer if they released 2 separate versions (stereo CD and DVD-Audio) as they did last time, but they may choose to do a Limited Edition release on the DualDisc/DVD+ format.
Guess we'll have to wait and see