why must everybody think that when Nikon/Sony/anybody does anything, canon needs to follow. that's not called leading.
Canon is following it's own plan. Lenses take years to develop and bring to market. What is being released now has been identified and funded years ago.
Since 2010, Canon has released the following FF lenses:
70-200 f/2.8L IS II
24-70 f/2.8L II
24-70 f/4L IS
Most of the lenses in the longer focal range have been updated recently, and it doesn't take an oracle to see that Canon will be replacing older lenses, shorter focal lenses and lenses that have more competition over the next few years. Canon gains nothing for not bringing out a better design that they can sell for more profit than an existing model.