I mean, I'm pretty sure we had this debate in these forums a few years ago, but that didn't stop PHI from trading with us (#1 for #3 + Another 1st), nor did it stop Cleveland from trading with us (Irving).
Also, I think if SAS is serious about shopping Leonard (he's not willing to sign an extension), they'll CERTAINLY give Ainge a call to gauge interest. Celtics won't trade Brown or Tatum for him, but Spurs will still just ask I suppose.