Sure, I still would buy it. I'm just entering the av world as I have been a computer nerd for some time. In computers, after 3 years, your computer is old and obsolete and needs to be replaced. The HD-DVD player is cheaper than a computer and provides me a great service of high quality audio and video. There is always something better and/or cheaper for those who wait.
If BD catches up and passes HD-DVD, then when it does and becomes successful, I will upgrade and I'll have a better product since the quality is as good and it would be a 2G+ machine.
Just because the old thing was good enough, doesn't mean the new technology will fail. Let's look at some examples. Dial up internet service is good enough for many users, but has that prevented me from enjoying 8mbit cable? Car manufactures make vechicles that go from 0-60 5 sec (I'm guessing), when in reality 0-60 in 15 sec is probably good enough for average people.
I highly doubt that this format would last 20 years much less 50 years and remain a premium product. 45gb in 20 years is going to be redicously small. I would estimate that thumbdrives will be that in less than 5 years. 20 years ago, computers had 20mb hard drives?
If you want to see if it is the time to buy, ask yourself this question. The enjoyment I will get from the pristine picture and audio over the next year is worth $10, $20, $50, $100, $200, $500? One way to estimate this value is to try to determine how much more are you willing to spend to rent/buy an HD-DVD over a DVD. Personally I would take $3 for renting. Then estimate how many movies you will watch in the next year, 2 per week or about 100 movies. Thus I would value it to be about $300. Once you know that, how much cheaper will HD-DVD players be in a year? $100, $200 dollars. If you value it more, then you should buy it, if not don't. Following this simple rule, you will get the optimal solution. I bought it. (For the record, I didn't go through much logic, it was more of a compulsive buy)
Hope this helps.