A few thoughts.
First, the logic that Ainge should trade away three plus assets (some with years of control) for the opportunity to have George play in Boston for one year so that the C's just might just beat Cleveland and then lose to Golden State is kind of stupid. It appears tthat George had no intentions of signing an extension or I suspect Ainge would have pulled the trigger. But as DrewDawg says, we just don't know.
Next, this should raise the odds of CauseWayward coming to Boston. Yet another team in the West got better, at least for now, and unless Gordon is also good buddies with Rubio, he is losing one of his friends from the Jazz in Hill.
Finally, the Celtics aren't out of options here. One thought (forgive me SRN) is to explore what it might take to sign Andre Iguodala while maybe exploring an individual trade for one of Crowder, Bradley or Smart.
In any event, I am ok if the C's run back the same squad in 2017-18. They may not do as well but even with Hayward and George plus a gutted bench, they weren't likely to go much further than they did this year. And it would sting if George simply departed for LA next summer and the C's had nothing to show for it.