There are at least two ways to view this situation:
1) OKC reaching the conference finals maybe eliminates the tiny sliver of hope Celtics fans had of acquiring him this summer.
2) OKC's (likely) WCF loss to GS helps KD realize that GS is the team in West for the next several years, and that he doesn't want to waste the rest of his prime playing in the same conference, so he looks to the East and sees Boston's golden shores and Brad Stevens' pearly smile welcoming him to his new home.
Unfortunately, there is a 3.
GSW destroys OKC and Durant decides that if he can't beat them, then he might as well join them. At that point, we should all just sit back and enjoy GSW domination over the basketball universe.
People keep talking about that, but I really don't think it's a feasible option.
First, there is such a thing as "too much of a good thing." If Golden State repeats in convincing fashion, they legitimately would have to consider whether or not adding Durant is a smart move. As the saying goes - if it ain't broke, don't fix it. Durant is obviously an All-NBA talent, but adding him could very well have locker room/stylistic issues if he isn't ultimately happy being a second option.
Second, I don't think Durant would truly consider Golden State anyways, because he has too much pride (in a good way not a bad way) to go to such an established team like that in his prime. He would play second fiddle to Curry, and his legacy as a top-dog would ultimately be severely damaged by going there.
Realistically, I just don't think he can go there if for the sake of his legacy. He'd damage himself too much by going to join a repeating champion with three All-Stars, three probable All-NBA players, and a repeating two-time MVP while he is still in his prime. I just can't see that happening.