The C's aren't dealing Horford or Hayward in an AD deal, period.
Both guys are the first two marquee FA signings in C's franchise history, which to me seems to hold a little more weight than people think. Also, I agree with what @nick said earlier (or was it Roy?), if Horford sensed that the C's would trade him to a non-contending team like Pelicans, he probably would opt-out.
Hayward meanwhile has looked better lately and I think he's essentially untouchable through this summer as it would look bad for the organization if they dealt him just a year after the season he suffered that gruesome injury (Hayward did leave a good situation in Utah to come here). Also I think Brad would vouch for keeping Hayward for the next few years.
And lastly, NOP wouldn't value these guys as much because of the $$$ they make and they prefer to stock up on younger pieces and future picks. So either way you'd have to do that and I guess my point is, why would WE want to give them up if we're also serious about competing for a championship. Like most have posted, even if you give away Hayward/Horford for salary, you're still likely giving up Tatum, Grizz Pick, and a few other young pieces or picks...
Also, you see Stevens say it, you hear Tatum say it, even Kyrie and many others, Horford is the glue-guy on this team and probably the most important team-player. When he plays well the team wins a ton of games and his positive play has a trickle-down effect on every player alongside him on the court. He's also one of the better defending bigs in the league and is an Embiid-stopper seemingly.