Personal opinion is sooner they do the better. Better pic quality, sometimes get extra features, will last longer than vhs, easier to store. I reckon 5 years from now it'll be almost all dvd, that's why you can now buy top spec vid players for next to nothing, well you know what I mean!
they already have. there are several DVD/VCR combi's on the market. which would seem to be positively encouraging pirating DVDs to VHS, as 99% of porn DVDs have no copy protection.