Canon patent for a 50-300mm F4.5-5.6 lens with diffractive optical elements. The optic formula described in the patent appears to refer to APS-C sensor (not full-frame). Hence, the lens may come either for EF-S or EF-M mount. I guess this would be the first APC-S oriented lens with diffractive optics (anyone?).

• Patent Publication No. 2016-57444
  • Published 2016.4.21
  • Filing date 2014.9.9
• Example 1
  • Zoom ratio 5.59
  • Focal length 51.77 135.00 289.53
  • F-number 4.65 5.05 5.85
  • Half angle of view (degrees) 14.78 5.78 2.70
  • Image height 13.66 13.66 13.66
  • The total lens length 126.05 169.37 184.15
  • BF 35.50 35.50 35.50
• Example 2
  • Zoom ratio 5.90
  • Focal length 49.13 135.00 290.00
  • F-number 4.65 4.95 5.85
  • Half angle of view (degrees) 15.54 5.78 2.70
  • Image height 13.66 13.66 13.66
  • The total lens length 108.00 152.12 168.00
  • BF 15.69 15.69 15.69

[via Egami]