If you've not seen the thread on dpreview Oly let slip on their european site of an E400 and also that the E400 name has been registered by Olympus. No real information at all other than that. Whether its an upgrade to the E330 and so soon or an upgrade to the E500 is any ones guess. Here's the links:
The original note to the E400 has been removed but one of the posters in the thread below took a screen shoot of the page.