Thanks to all the hard work we've done in the past months, the next version of Drupal will have a lot of great improvements!

improved logging functionality
support for reverse proxies
many language system improvements (support for right to left languages, advanced language detection, support for translating posts to different languages, etc)
improved handling of teasers
drastic theme system improvements
an improved installer
support for OpenID
and much more

There are also a ton of API improvements that should lead to more and better contributed modules.

As usual, we can't say when Drupal 6.0 will be ready (it's ready when it's ready) but it is estimated that it will take at least two months before Drupal 6.0 can be released.

More Here.