As everyone has stated, it depends on when, how and to whom they lose is the question. I think they have to at least reach the Finals, but if they reach the Finals and don't win, I would consider this season a failure. This team's window won't be open very long because the secret is out: OKC knows how to draft and develop at every level, so GM's are gonna pay big money to pry our bench and developmental players away. Also, the way the salary cap is set up, we won't be able to keep all of our players and draft picks, one of them has to go.
The reasons why OKC lost against Dallas last season:
1) Chet and J-Dub, moreso, disappeared offensively, putting more pressure for SGA to score.
2) SGA struggled because after Dallas took away the midrange game, he didn't have the 3 point shot in his bag.
3)The role players 3's stopped falling... and players like Dort, Giddey and Jay Will either couldn't hit or were reluctant to take midrange jumpers.
4) The stretch bigs made life in the paint and on the 3 point line difficult. No rebounding, Chet constantly getting his shyt tossed back... and PJ Washington shooting like Steph Curry.
This season, the players from last season's team have (hopefully) addressed those issues and the added pieces from the trade, new signing and draft should put OKC over the top.