According to rumors from CR, the next version of EF 16-35mm f/2.8L lens will be released sometime in 2016. The focal length could change slightly, something like an EF 15-35mm f/2.8L USM was suggested.
Canon has changed focal lengths a couple of times for this kind of lens. The first in the line was the EF 20-35mm f/2.8L and then the EF 17-35mm f/2.8L and most recently two version of the EF 16-35mm f/2.8L. Event photographers still crave the fastest lens possible for the job, and the EF 16-35mm f/2.8L II could use a performance refresh.
The release date for this EF 15-35mm f/2.8L USM lens will be in 2016, after the rumored next wide-angle prime lens EF 35mm f/1.4L II USM, which is rumored to be announced in Summer 2015.
via: CR
Read More: Canon Rumors