Hell no!! I have a very large collection of DVDs. I would have to sell at a huge loss. I have pretty much stop buying DVDs, though, due to the fact there are rarely must have movies coming out.
Another point you should consider: are all your movies going to benefit from HD-DVD? Consider the source material. Some of the old titles did not benefit in quality going from VHS to DVD. Of course, DVD is a far superior storage medium so it was a no-brainer for most to convert. Do you think all of your DVD movies going to benefit going to HD-DVD? Is even a slight marginal gain worth a repurchase?
I remember trying to convince a friend, who likes to rent and rip DVDs, that it's not worth trying to rip DTS all the time. In one example, there was a movie that had option for both Dolby Digital and DTS. With DD he could fit it on one blank, with DTS he would have to split it to two discs (using no compression). Of course he chose the latter, wanting to preserve the highest quality transfer. It so happened that the movie was a drama and most of the sound is dialogue directed at the center channel. I can understand for newer movies with special fx, lots of actions, explosions, and etc, but for non-action movies with mostly dialogue it's overkill.
I've seen it in videogame consoles all the time. Some of the games for the next-gen consoles like PS2 and Xbox were rehash/port of games from previous systems with absolutely no improvement on the predecessor.
Not all movies are going to benefit going to HD-DVD. People should look at their collection and evaluate title by title whether it is worthwhile for an upgrade.