I certainly see your point about the 5DMKII, which is a fine camera (I had the 5D prior to that). But I've had it for almost 4 years and I'm tired of it. I was wanting something new. Something revolutionary. I am a landscape guy that does large prints so I do have a D800e on order, but I decided I didn't want to wait on Nikon to deliver. The 5DMK III is a dream at high iso speed and low noise at just about any ISO. The new AF is more like my 7D which I have used for birds in flight. I came from a 10D to a 20D, skipped the 30D, then 40D, then 50D, then 7D, and then 60D to get the articulated screen for low level macro work outside before going to a field monitor using tilt shift lenses.
Now that is me, but what about you. Do you shoot raw or JPG? Are you up to speed on the latest photoshop or lightroom? What type of L glass? What are your subjects? Do you do macro, tele, wide angle, low light, or wide angle - how wide? City, people, or scenery?
I hope you see where I'm going. Without knowing more about what you shoot and how you shoot, I'm feeling like saying that a jump to a full frame anything will be quite a change. Not to mention that you will lose your 1.6x crop factor so lenses that had worked fine on a 30D, may not fill the right focal length using a full frame camera. Lenses that look pretty good using a crop camera can take a real quality hit on the edges of the frame on a full frame camera.
This is my guess and suggestion, buy new tech if you can afford it. It may take Canon another 4 years to deliver the next generation of 5D. In another four years, do you really want to end up being 8 years behind the tech if you bought the 5DMKII now? Just for messing around shooting people at events I take my 60D because it is new, it is fun, and I'm not risking as much investment should it get banged up or stolen. I like all my Canons but the 5D MK II will not be getting much use anymore except as a backup camera for the 5D MK III. I'm really enjoying the new auto iso for interior shots. Better color and cleaner images and better auto white balance. It is a blast.