Short answer. Yes. But not until you test your theme on WP 3.0 on a separate install of WordPress.
WordPress 3.0 has been long anticipated by many of us in the web design and WordPress development field. It takes the best of WordPress and WordPress MU and merged the code base. Do some research on this and please do not upgrade your WordPress site until you are ready. Expect to have downtime, as links may break or your theme may need to be tweaked in order to work in WP 3.0.
This is a big step in the write direction for web sites world over, you will need more and more sites managed by WP and blogging platforms merging with content management, eCommerce and more.
Mahalo Matt Mullenweg and team for your foresight and dedication to this project.