OKC is definitely opening up if the Thunder don't make it to at least the WCF and it's probably a couple of years overdue. Brooks is not a good coach. The Thunder are starting to get a real Cleveland circa 2008 feel to them. Despite having the best scorer in the game and an elite second option they still are extremely predictable offensively. The Thunder's offense has long been extremely isolation based and once their initial look is stopped they have very few counter actions that they run. The fact that it took Brooks three games to realize that he should play Reggie Jackson, the only other guy on the team who can get his own shot, over the 39 year old Fisher speaks for itself.
I'm sure Kevin Ollie's name will be mentioned for that job, but like you said, whoever takes the job is going to have two years to win a title. Trying to do that while putting together a staff and learning the NBA coaching ropes on the go would be quite the challenge. The Wizards making the ECF's this year is also bad news for the Thunder. People are already starting to push the Durant coming home to DC angle. No premier free agent would have ever seriously the Wizards as a contender but all of a sudden teaming up with a Wall-Beal backcourt looks pretty tempting.