At the end of the day, it all depends on two things.
1. Does Irving actually sign an extension here (Boston) long term in 2 years?
2. Does Cleveland win a Finals this year? (Or next assuming Lebron stays put)
If Irving doesn't sign an extension here (bolts) and/or Cavaliers win a Finals within the next two years with Isaiah and Crowder (maybe Zizic) having a role, then Celtics lose the trade. So far though, C's are slightly winning it, though it depends where that BKN pick lands and what happens with Zizic a few years down the line.