More or less 2 weeks ago the image above showed up on kakaku.com, disappeared shortly after, and was spotted and shared by digicame-info.
It appears, at least I have been told so, that the lens is real and should soon be announced. This comes from a source that was _not_ always right in the past, so take it with a grain of salt. However, a lot points to the fact that we have a serious rumor here. First and foremost, the pic looks truly authentic and not photoshopped. Second, there is a patent for a 11-24mm f/4 lens that surfaced some time ago (January 2014). Third, I have this source insisting that it will be announced soon :-) In one word: the picture of the lens appears to have been a real leak, for whatever reason.
To some degree all this copes well with a long running rumor suggesting that Canon may eventually announce an eagerly awaited (and much rumored) high resolution DSLR. Recently, even Canon itself mentioned the development of a high resolution sensor in an interview with Mr. Masaya Maeda, Managing Director and Chief Executive, Image Communication Products Operations at Canon. The EF 11-24mm f/4L could be announced together with this high res camera. While I still have some doubts about the high res camera, I think the 11-24mm has a very good chance to be real.
Stay tuned. Your comments and thoughts are welcome, let me know in the comment section.