While the new CBA hasn't been officially released, one new nugget that's supposedly in it is called a "designated veteran extension." The current CBA has a designated rookie extension, that allows one rookie extension during the length of the CBA to be signed for 5 years instead of four, and potentially for a higher dollar amount than the 0-6 max if you meet certain performance qualifications. Examples of players who've signed such deals include Russell Westbrook, Kyrie Irving, Damien Lillard, and Anthony Davis. Kevin Love's divorce from Minnesota started because they wouldn't give him the 5-year deal (they wanted to save it for Rubio, which was not wise.) It really helps keep star rookies with their drafting franchise, discouraging them from ever testing free agency after their first contract.
From what I understand, the designated veteran extension will operate similarly. It will let the team offer up to the 10-year max salary, even if the player does not have 10 years of experience. This would have been helpful for OKC to potentially keep Durant. It also will allow a team to offer it even if over the cap. Previously, if a team was over the cap, the new contract could start at no more than 7.5% more than the most recent season. If the parties wanted to create a larger raise cap room needed to be sued. For this one special designated veteran, however, a large raise can be given even if over the cap.
This can both help and hurt the Celtics. The bad news is that, if this extension truly exists, it is unlikely that the Kings will trade Boogie until he rejects their designated veteran offering. In other words, if Boogie comes on the market, it won't likely be until next summer, and there's a greater chance he stays in Sacramento, due to the max salary advantage offered by this new rule.
The good news is that if the Celtics want to extend IT (or AB), they can do so next summer after spending their cap room on free agents. What isn't clear to me is if a max deal is required for the designated veteran (it is for the rookie version). I'm a little hesitant on paying IT the full max, personally, unless ownership gives Ainge a very large budget that includes significant luxury tax payments. Which they might if we score another max free agent this summer, and if they're willing to spend big, all the more power to them.
Anyway, I find this new part of the CBA most interesting, and I would be somewhat surprised if Ainge didn't use it this summer on IT.