Extensions lagging behind Firefox releases

They do get quite a bit of advance warning, through news sources, nightly builds, betas, release candidates, and the Mozilla Developer Center (http://developer.mozilla.org/).

Unfortunately, a lot of extension developers still wait until the last minute to roll out updates, or may simply stop supporting their extensions altogether.

Keep trying to update your extensions, and also check with the extension developer's site for a beta version that might not yet be posted to addons.mozilla.org.

Some extensions may actually be compatible, even though they haven't yet officially been released for 3.5 yet. If you are desperate to get them working or feeling adventurous, you can try overriding the version compatibility checks, but keep in mind, this isn't supported by Mozilla or the extension developer, and if the extension really isn't compatible, or hasn't undergone enough testing, you may break things, and in rare cases even lose data in your profile. There are tools for power users such as MR Tech Toolkit (https://addons.mozilla.org/en-US/fire...) or Nightly Tester Tools (https://addons.mozilla.org/en-US/fire...) that make this easier, but be careful and be sure to back up your profile!