I've been looking at the 330 and 510 also--- but having to wait for Ikelite to start producing the housing for the 510 is a definite drawback..
I did contact Ikelite about it and here was their response:

Missy,

It's too early. We plan to offer a housing for the Evolt 510, but we have not yet assessed the camera. Please check back in 3-4 weeks.

Thanks for the inquiry.
Regards,

Brett Foster / Ikelite