I would think SD DVDs are going to be around for a long time. Most people won't be buy a blu-ray or HDDVD player and HD display for some years to come and you can be sure that, although there will be many titles initially released in HD, and perhaps in 2 or 3 years all new releases will be both SD and HD, release of older movies will be slow in coming. Even now there are many titles which have yet to be released on SD DVD, delicatessen comes to mind.