Pony (not Sony), has announced the spec for a hybrid Blu-ray / DVD disc to potentially release films on both formats with a single disc. Unlike the HD-DVD/DVD hybrids of 2007, these discs contain both formats on the same side of the disc.
There are drawbacks. The first generation discs are capable of carrying DVD-9 data, but only 25Gb Blu-ray. The price is also quite high at the present. The disc meets the Blu-ray spec, but has not yet been approved by the DVD Forum until compatibility can be confirmed.