having the deal fall through is a bad look for both sides, which adds incentive for the deal to go through.
but, if it does collapse completely, it is the cavs who will suffer more in the long run. 
celtics - 2017-18 is in trouble since IT will either miss part of the season or sold off for lesser return. the celtics will make the playoffs, but get bounced early, maybe in second round since they lack a very good scorer to compliment hayward.
crowder is gone one way or the other. 
but, after that, the celtics have the brooklyn pick back and get a year of development from the youngsters. IT would have been gone anyway after next season, so no change there.
not doing the trade hurts the celtics for next season, but the celtics can recover and with the youngsters can look very good for the years following.
cavs - kyrie is not suiting up for next season since they really need to/have to trade him now. compounding this problem is that any sort of leverage they may have had will be reduced greatly. what can they get for kyrie that gets them closer to their twin goals of (1) competeing this year, and, (2) starting the rebuild after lebron leaves?
the boston deal was a god send for cleveland to gives a final shot at a championship AND jump start the rebuild. 
i think the deal goes through, with perhaps some tweaking by boston.