Dual-layer, certainly yes, that's always been a feature of DVDs.
Double-sided? I'd say no, I don't see how a disc could be flipped over inside the machine, and they are rare enough I don't think they'll go to the extra work to build that feature in.
But because they are rare, and even more rare are dual-layer, double-sided (most made this way, Farscape comes to mind, had a huge number of defective discs), so the most you'll see is dual-layer on one side and single on the other. It is easy enough to copy the single-layer side to a DVD-R and store it as a separate disc if you really want to watch its content.
