Couple people mentioned we should throw money at him in the summer instead.
#1 - I'm not convinced philly lets an asset walk. That's a reach. He's arguably their most valuable player and they are struggling to get to the salary floor. My guess is they match any offer and work out a trade afterwards even if it's pennies on the dollar. It would be moronic to let him walk for nothing. Embiid is expected to be on a minutes restriction but even if he were to flourish in 40mpg ... And even if Simmons played PF (most expect him to start at SF), and even if Noel racked up a season of DNP's, he's shown enough defensively that teams are still going to have interest in trading for him two seasons from now.
#2 - keep in mind that if you trade for Noel now, you can be the team to give him his qualifying offer next summer - which means you'd have a period of time where'd you still have cap flexibility to go after someone like Gordon Hayward. Whereas, if you plan on just offering him 10+ million this summer, targeting another max salary no longer becomes possible because you would be eating too much salary in your Noel overpay. So decide if you'd rather have Smart + Noel (which probably isn't happening anyways because philly will likely match any offer) or Potential Max Contact (Hayward? Blake? Durant?) + Noel.