Who says no?
http://en.yibada.com/articles/150327/20160810/nba-trade-rumors-76ers-knicks-working-out-jahlil-okafor.htm
O'Quinn and Justin Holiday will do very little to improve Philly's roster; and if they want to take a gamble with players of this calibre they do not need to give up Okafor for them.
Based on this, I would say Philly says no, but then the site says
and a future draft pick
Since this is clearly the most valuable item from Philly's POV in the trade it is absurd that the site does not specify which pick this could be. Having said this, even in the best case scenario (2017 pick: NYC might be a lottery team, draft is only a year away, and the draft is considered to be good) I still think Philly says no: why give up a good prospect with still three years on his rookie contract for a potentially non-lottery pick? Especially if you are Philadelphia and you have future draft picks running through your ears? And you know you won't be able to re-sign all these young prospects you already have?
I mean, Philly already has 3 first rounders (all of them prolly lottery ones) for 2017 (their own, LAL protected 1-3 and SAC's) and lots of second rounders 2018-21. If they are giving up Okafor it will be for players of proven value (this value might be mediocre but it will still have to be proven instead of picks or risks such as Holiday).