I use the 24-70II (and the 70-200II) a lot. But I also use the 35 f1.4 (Sigma) and the 85 1.2L II (and a few other primes) a lot also . The zoom is excellent and very practical. The volume production is done with the zooms. But I get this hard-to-describe feeling of being more creative with the primes. I think more, I move more, I spend more time on composition and framing etc. When I look back at a year´s shooting, when I´m going through all the images during Christmas break, it´s almost always pictures shot with the primes that stand out.
So I will continue to look for improvements in newer versions of the various lenses (I hope a 85mm f1.2L IS III, with improved AF speed is next), but I will always have a combination of primes and zooms. For a zoom to make a prime obsolete would mean a 24-70 f1.4L IS, which I don´t believe I´ll ever see.