The Expertise Cap for Retribution Paladins did indeed change with Patch 4.0.1. Ghostcrawler said it was an unintentional change, and the Expertise Cap should be back to 26 at level 85. For now, it seems we only need 23 Expertise to reach the Expertise Cap! [Source]
Due to recalibrating expertise for Cataclysm, level 80-83 creatures (which includes bosses) dodge and parry less, so you need less expertise, 23, to be exact. Sorry we didn’t announce this. I would classify it as an unintended consequence (though not unknown) and not a desired change on our part.
At level 85, you will need 26 again.