With Morey you can't rule out anything but if he were to trade one of the stars it would almost certainly be for an equally big star, and that's probably a short list. A lot of the stories I've read this week also talked about how suited Joel and Simmons actually are to Morey's philosophy, because Joel generates a ton of high-percentage close-in points, while Simmons is a three-point generating machine (just with assists, not shots).
Moving Horford to make room for shooters/spacers is still the key but I do think that, even with Rivers having had success with him, Morey coming on board makes it more possible they trade Harris, because he has no ego invested in the original trade/signing, and he's more likely to go bold. Richardson could still go too.