The first thing I have to say about this is keep your worpress up to date at all times! Skipping a release will not only make you vulnerable to hackers, but also make it more difficult to upgrade later. But this, of course is something you already know, lets see what we could do to make it easier to manage this.
Wouldn’t it be nice if you had a distribution system for wordpress?
Actually, you have! You can use Subversion to install wordpress, and upgrading later is as easy as just switching repositories, if you follow static versions, or svn update if you install from trunk.
This makes upgrades a 4 step procedure (you can cut it down to 2 if you like to live risky, or if you don’t use custom plugins):
- Disable all plugins
svn sw http://svn.automattic.com/wordpress/tags/2.5/
- go to your wp-admin, and update database (one click operation)
- Enable your plugins again
As mentioned, you may skip the first and the last point.
See wordpress.org for more info, on how to switch from a tarball installed wordpress to a svn-installed wordpress, or performing a fresh install from svn.