While you can get a 3dfx card still, it could be very risky. Previous history shows us that when this happens, it's over. No more drivers, and very limited tech support. When companies like Canopus and Diamond stopped, you could still get reference drivers from the chipmaker. But, when the chipmaker is the boardmaker, you are pretty much screwed out of any future drivers, or future versions of DX support. When articles say driver support will stay with 3dfx, that is a bad thing, and is a way of nVidia saying they are not going to support the 3dfx cards. So, driver support will only last a few months, then 3dfx will be no more.
NOTE: nVidia is NOT buying 3dfx. They are only buying the companies assets, and once all is sold, and the loose ends are tied up, 3dfx will shut down on it's own.
Only get a 3dfx card if it meets all of your needs as it ships today, and only if you could care less about future needs or support. Also, don't be surprised to see the $150 card priced below $80 in the next couple months until all remaining stock is gone. All we have to do is look at history.