Tomorrow is the day Canon makes its big Hollywood announcement. Just for fun I am going to put up my own predictions. I have no information bar the constant chatter on the Interweb

It will be a camera announcement not just a new printer. I think the new Hollywood facility is evidence that Canon is trying to create a new market for itself.
I think this new segment will mean a range of cameras with different abilities. Typically Canon video cameras come in two versions - one with a more limited feature sets. I expect there to be more variation this time.
A PL camera with an S35 4k chip. I expect it to have an F3/XF305 form factor and facilities. On camera recording may use Canon existing 50Mbps MPEG2 4:2:2 codec and be 1080p. I think 4k will be off board only, possibly extra like S-LOG is on the F3. Price will be somewhere in the gap between the F3 and the Epic X. I expect them to have a way of adapting EOS lenses to work. It would be almost embarrassing not to when the Epic can.
An EOS camera using an adapted DSLR sensor and electronics. The 1DX is the only next ten chipset near production but a crop sensor feels more likely. I also expect the codec and frame rates to come over from DSLR rather than the video line. I expect there to be a version with HDMI only out and a dearer variant with SDI. I think that there output will be clean 1080p but no more than 4:2:2. I think Canon will want to keep the pricing near the FS100. It seems a lot to squeeze into the diminutive XF10x line and borrowing from the XF30x line would screw up their range pricing. Either they are going to have to give it a brand new form factor or use the XF30x chassis and pitch it between the FS100 and F3. If they go the more expensive route then PL adaption is likely.
I don't expect either camera to look like a hair dryer.
I expect them to launch more cinema oriented lenses, though it may be a while before we see any ship as Canon has been very slow relaxing lenses recently. However, this may be the most lucrative prize for Canon. Not only is there a huge pent up demand for people having an affordable dedicated video camera that can use EOS lenses, Canon are also ruled out competing for lensing other manufacturers bodies. If Canon could do a "CP2" with their fast L primes and zooms like the 70-200f2.8 for a little less dosh than Zeiss, they would have a brand new revenue stream.

What would I like to see most?

A 5D Mk3 carefully tailored to my own wish list of course.

I would be tempted an EOS video only camera but even at FS100 pricing I would need to have to be serious about this earning some cash for me. It's still too much for an indulgence/hobby camera. I don't think we will see any successor to the 5D Mk2 till 2012 though.