Holy product leaks Batman! Info and photo leaks don't get much more comprehensive than this. In what they're actually titling the official introduction post, Canon Rumors has posted four higher res product shots of the Canon 100-400mm f/4.5-5.6L IS USM II alongside full specs, pricing, and a detailed description of the lens from top to bottom.
At this point, it would be a formality for Canon to even announce the darn thing. But if you want to save the surprise for the official announcement of this Unicorn lens, we don't suggest you read on.