Hi Jason, welcome to the Cameralabs forums!
Olympus doesn't currently produce any lenses with optical stabilisation for the Four Thirds body fit, nor any bodies with built-in anti-shake.
In fact the only optical anti-shake solution for Olympus Four Thirds bodies right now is the Leica 14-50mm lens which comes as part of the standard Panasonic L1 kit. Interestingly, the L1 also shares the live view of the E-330, so it might be the camera system for you!
It's quite a unique and pricey proposition though, so check our full review and video here:
We'll also be publishing a standalone review of the Leica lens very soon.
But the Leica lens is a standard range zoom and you mentioned wanting a longer focal length. So if you're after a longer focal length with anti-shake, you'll either have to go for an optically stabilised lens for a DSLR like an IS model for your Canon XT or a super-zoom all-in-one like the FZ-50. This is obviously the conclusion you'd already come to!
Between the two, it depends whether you want the low noise and quick response of a DSLR with a long lens, or the lower price and live screen of a super-zoom all-in-one. There's pros and cons to each approach and only you can decide which means most to you!
What kind of photos do you like taking and have you had any experience with an all-in-one before your DSLR - ie, could you swap back to one, or would you prefer to keep the feel and operation of a DSLR?