What would "tanking it" really look like here, though? Waiving all the veterans with expiring / non-guaranteed contracts and then signing a bunch of D-Leaguers to fill out the roster?
I doubt it.
It's not like Lee, Amir, Jerebko, Turner etc have a whole lot of trade value, especially if the team is doing as badly as you hypothesize. The Celts don't need another fist-full of low-value draft picks.
I don't think there's any reason to believe the team is gonna start playing the rookies ahead of the veterans if the team is struggling, either.
For better or for worse the team is gonna stay all-in on making the playoffs again this year. They'll give a lot of playing time to guys with no future here in the process, and the rookies won't get much opportunity to develop, but at least we can count on the Nets to tank for us.