In 2019, Rozier walks and the Clippers pick (if the Clippers have a similar year to the year they had this year) may turn into a second rounder. Sacramento may be a lottery Say #6 or so) and if the Memphis pic coveys then if means that its the ninth pick or worse, and our own pick will be, we hope, in the 30s. So there will be no "consolidating our picks and moving up". No one with a pick in the top three, in a purported weak draft, likely wants the 6th pick (Sacramento), and the 10th pick (Memphis) and the 31st pick to move up from 6 to number three. It's trading two dimes and a nickel for a quarter and everyone knows it. Meantime, the Celts don't actually want or have roster space for their own picks. They would be nearly forced to "draft and stash", whether they liked any of the Europeans or not. So, it is not unreasonable to try to maximize the value of those assets now.
The value for next years picks is that maybe an NBA star becomes disgruntled and forces a trade. Short of that, our assets that look so good now, will likely depreciate over the next year.