I think the dualdisc is a good idea in that it is intended to be universal format that can be played in either a DVD player or CD player.
Unfortunately, many CD players are not be able to play the "CD" side, and many DVD player manufacturers have put out warnings against using the dualdiscs in their machines.
One thing I noticed about the discs is they seem to be heavier and thicker than a standard CD or DVD. I think this may be the reason for the warnings from electronics manufacturers.
From looking at the dualdiscs that I have bought, they don't appear to be made as well as standard CDs or DVDs, either.
Personally, I think the best universal format would be the hybrid SACD which can be played in either CD, or SACD players.
I have not had any experience with DVD-A since I have yet to find any discs that I want to pay for.
What will win? I would put my money on dualdisc. The reason for that is whenever you need a universal format, the weakest usually wins.