Tomorrow is the day we finally see the Canon Cinema EOS C700, a camera that is apparently aimed squarely at ARRI. We first reported about this camera back in May, but haven't received any real updates on specifications since then. You can see that information here.
I also think it's possible that we'll see an announcement for at least one anamorphic cinema lens from Canon, though I can't confirm this.
The surprise for tomorrows announcement will be the XC15, a camera we know very little about specifications wise, but images of leaked a few days ago.
These announcements are for the IBC show, which starts late next week in Amsterdam.