The coming WordPress 2.6 (scheduled to be released on August 7th, 2008, or July 7th, 2008) will have more features. Most of you probably heard that about the probably-most-well-known Post Revisions feature. But, there are some other features that should be highlighted. Here are some of them I find (using WordPress from SVN, revision 8094):
Post Revisions

Using this, our WordPress will save a copy of our post everytime you edit it. We can take benefit when we want to revert our post. We can also compare or show diffs from two revisions. Wiki users should be familiar with this. This Post Revisions feature will be shipped and activated by default. If we think that we do not need this, we can deactivate it easily. Just add define('WP_POST_REVISIONS','0'); in our configuration file (wp-config.php). More info about Post Revisions.
Google Gears supports

Description from ticket #6965 tells about this:

First run. Support for Google Gears managed offline storage. The patch adds all static files used in the admin interface to a single offline storage. That speeds up page loading a lot, as it serves virtually all requests for static files from the computer’s HD instead of the network. So instead of 50-60 requests to the server on some pages, there are only 2-3.

There will be a new small link on the top-right navigation. It says “Speed up!“. Learn more about Google Gears.

Identicon, MonsterID, and Wavatar support

WordPress 2.5 already has built-in Gravatar support, and we have option wether we want to display it or not, and also set the maximum rating. Automattic already acquired Gravatar in October 2007, and they added interesting features on it in last April: Identicon, MonsterID and Wavatar. If you’re using that by installing plugins, they will be shipped in the packaged.
Press This
Actually, this is not new, but should be featured. Take a look at WordPress Codex for more details. In short:

WordPress makes it easy to quickly add links and information to your site through the use of a bookmarklet called Press It. A bookmarklet looks like a link in your Favorites, Bookmarks, or Links list but it is much more powerful. It adds the capability to quickly create WordPress post entries on the fly while working on the Internet.

It seems that this feature called Press This, but the Codec says “Press It”. Okey, don’t get confused. It seems “Press This” is the correct one.
What else?

• wp-config.php can now be located one-level up from the rest of your WP install if you want to move it out of your doc root. (source)
• Shift-click to select a range of checkboxes — Everyone loves how you can click a checkbox in gmail and then shift click another checkbox farther down the line to select all the checkboxes in between. (source)
• Word Count — Add word count thingummy to the Write Post screen. Should work in Visual view, Code view and tinyMCE-just-plain-off view (source)