Although I suppose you could fake it by taking a DVD-18 disc, using one side for a standard DVD-9 disc, and using the other side for a BD9 disc. (Of course, that's an ugly kludge, plus you'd probably only have room for bonus content on the DVD-9 side...)
I still suspect that the only real reason Blu-Ray beat HD-DVD is because everyone with a PS3 automatically had a Blu-Ray player also, while no popular consoles came stock with a HD-DVD drive. I suspect that if the XBox-360 HD-DVD drive had come built in instead of being an expensive extra that HD-DVD would've had a much better chance, especially considering that HD-DVD has no region encoding (Blu-Ray does), and HD-DVD offers "flip" discs that can be used in your new HD player /or/ in, say, a portable DVD player, or one mounted in a van, all for the price of just the HD disc. Haven't seen anything like that at all for Blu-Ray yet.