There is no option to be picked up.
There was an option and Ainge declined to pick up in November which is what I referring too. Ainge declined to do so. I said if Ainge liked him so much, why didn't he pick it up?
https://www.bostonglobe.com/sports/celtics/2016/11/01/ainge-gives-reasons-for-not-exercising-options-young-olynyk/VKNl3EcEVwRkDOvdTYwBZM/story.html
That's not an option, it's an extension. 1st round NBA rookie contracts last 4 seasons: 2 guaranteed (in Kelly's case, 2013-14 and 2014-15) and two team options (in Kelly's case, 2015-16 and 2017-18). There is also the ability to extend the player at the end of the rookie contract, which seems to be what you are referring to. This is VERY different than an option, though.
An option would mean that the team decides to pick it up and, boom, that year is locked in at an already decided rate (it's decided when the contract is initially signed). An extension is essentially signing another contract before your old one runs out. Danny didn't do that with Kelly this year because it would take away cap space for this summer. That certainly doesn't mean that he doesn't plan to resign him - Danny didn't extend AB either. Actually, I don't think he's extended any rookie since Rondo in 2009.
Looking further into it, only 8 players from the 2013 draft got extended (and half of those were max guys: McCollum, Steven Adams, Giannis, and Gobert, who were all obvious choices). Guys like Otto Porter, Alex Len, Nerlens Noel, and Kentavious Caldwell-Pope also didn't get their contracts picked up. Do you think their teams all plan to just let them go? Of course not. They'll become RFAs this summer, just like KO, with a high chance that they end up right back where they played this year (just like KO)
You don't have to like Kelly, but don't make stuff up/horribly misrepresent things to try to justify it