The Celts have up to four first round picks in the 2019, a draft year that is supposed to be a weaker class than 2018. In addition, Sacramento could get Doncic and, coupled with their young talent, could be a little better. And the lottery rules will lower the likelihood that picks move up in the draft. So let's say the Kings pick is #5-7. Who do you get in 2019 that will impact your team? And what value, even if it conveys, is the Clippers pick at #15? And what about the Celts at about #30? Not much value for the Celts, and not much value in a trade for an impact player. If fact, you might just end up saddled with a guaranteed contract on a guy who doesn't help much for, at a minimum, several years. When you are in the luxury tax, that actually is counterproductive rather than helpful.
With the way their roster is constructed, the Celts need a few second round picks so they can get non-guaranteed contracts rather than late first round picks and ideally they'd get one more impact player from the draft within the next two years. I think the Sacramento pick in a weak 2019 draft year is unlikely to accomplish this. The pick that has, in my opinion, the highest "upside" is the Memphis pick (We should all hope that Memphis really sucks, their pick does not convey, and becomes unprotected or high lottery in about two years). The Memphis pick is the one we should hold on to.
If my logic is correct, the time to maximize these assets is this year. Package these picks, excluding Memphis, with Rozier and move up this year. The 2018 draft is deep through about 10-12 picks, and get a young big who can complete this roster. The most obtainable target is Bamba or Carter (you won't be able to get high enough for Jackson Jr.). Lets go; make the move Danny.