"...Gmail is a big system with many components -- there is no reason that Google would ever need to do a "complete" rewrite. That said, the individual components are frequently rewritten, and it already supports at least 4 completely different interfaces (AJAX, plain HTML, XHTML mobile, Java MIDP mobile, POP3, and probably others that I'm forgetting or can't mention). Adding a new UI for Joel's magical library wouldn't be a big deal."

Edit: Made title more interesting (but a little long).