I don't see it. No new version, no button to switch, nothing.
However, it has also stopped giving me the "Gmail no longer supports this version of your browser; please upgrade" so maybe that has something to do with it.
That said, I'm currently using a theme that changes with the weather outside -- I'm in a windowless office and the variety is nice. Am I going to lose that option when my work computer finally upgrades to the latest version of IE? (Which will probably be next week when I schedule my Windows 7 upgrade.)