According to the Nikon Rumors, Nikon may announce a new Nikkor 24-70mm f/2.8 lens in the second half of 2015 along with Nikon D5. This new 24-70mm lens may feature with Phase Fresnel (PF) element (diffractive lens).
If Nikon uses the PF lens in the next 24-70mm f/2.8 lens, the size and weight will be significantly reduced. And adding VR will make this a very desirable lens for every Nikon shooter.
Nikon already has a new patent for this lens, see below:
Read More: Nikon Rumors