In fact, Microsoft originally promised to roll out Denim, for the Icon specifically, by the end of 2014.  Joe B. from Microsoft announced in December that Denim was coming to the 928 and the 822 in December and that it would roll out to the Icon in "early 2015".  This was a ruse to slow walk Icon users.  Denim for the 822 and the 928 didn't include a firmware update, just an OS update.  It was Denim in name only.  This gave the appearance that VZW had tested and approved the firmware update and that it was just a matter of rolling it out.  The truth is that Microsoft was never able to get Verizon to approve the Cyan update for the Icon, and there is no evidence that they are having any better luck getting them to approve Denim yet. 

I won't believe Denim is coming to the Icon until I see it actually installing on my phone.