Postgres?
 

Well, in my experiences with MySQL and Postgres, MySQL servers have a real annoying tendency to always go down, as it's greatness is dwindling away, while Postgres is emerging to be very great. I was reading up on a few articles, and decided to use it on my own computer, and man, the server load lightened like crazy. Anyhow, I know that it does not support it (yet?), but are the dev's working on it, because I am getting dead sick of MySQL.

That would probably be a better question for vBulletin.com the dev's usually check and answer these things there ;)

This is true, I suppose. I think I might have meant to go to vbulletin.com, lol.

Even if someone wrote a vB database class for Postgres, a lot of the queries inside vBulletin would need to be changed. My guess, is that this might be something planned for vBulletin 4.

I personally (and many others) don't have those issues with MySQL.
Maybe it's a good idea to check also what's wrong with MySQL or contact MySQL dev team if there is a real issue?
If you did not build MySQL yourself, sometimes it's a good idea to do so. This way you know you get all proper libraries linked and other things.

I think additional database support may be planned for vBulletin 4.

I want to point out the keyword, think. People often mistake this as "x is planned for ..."

It would be nice to have multiple database types...

The dev team did say somewhere (!) that they were looking into supporting other databases "sometime in the future". (This was a while ago.)