DVD-R is definitely here to stay, since it is featured in the Pioneer, Panasonic and HP drives. However, they all use different rewriteable formats: DVD-RW, DVD+RW and DVD-RAM. DVD-RAM is going to lose because it can't work on standalone video players.
I would bet on Pioneer's DVD-RW since they already have a standalone DVD-Recorder, plus lots of units in Macintoshes.