Although the DVD Forum isn't really united behind this issue, it still seems that MPEG-4 will be the technology that is used in next generation DVD-Video discs. Opposition in DVD Forum wants to use existing MPEG-2 as a compression technology, but use upcoming Blu-Ray, bluelight laser DVDs, as a storage media. The proposed MPEG-4 usage means that the discs will stay in exact same format as they're now, using red light laser and 9GB / side (dual layer) DVD discs.
Even that DVD Forum decided that MPEG-4 w/ red laser is the standard for HD-DVD, its not sure that it will be also in "real life". If Blu-Ray devices gain enough popularity and achieve big portion of the markets before we see even a single MPEG-4 capable traditional DVD player, it is pretty clear that Blu-Ray has to be taken seriously also in read-only world (Blu-Ray is originally intended for recording markets).