No one really looks at the 2011 Mavs as one of the greatest teams ever. They sputtered into the postseason with a 4-3 record in April. They were a 4% favorite in Vegas to win the title, behind all of the Lakers, the Heat, the Bulls, the Spurs, the Celtics, the Thunder, and the Magic.
It'd be an amazing playoff run, but I think the distinction of "greatest teams ever" necessarily includes the entirety of the regular season and the postseason. You have your teams like the 2011 Mavs, who had a relatively pedestrian regular season (57-25, 3rd seed), but then had an amazing postseason marked by ridiculous comebacks in every single round. You have your other teams like the aforementioned 2007 Mavs, who flamed out in the first round after winning 67 games and having their best player win MVP. Truly great teams should show a consistent level of dominance throughout the entire year.
Short of OKC going on a Warriors or Spurs-like run and finishing the second half of the season something like 37-2, I think, at best, they'll have to settle for "one of the greatest playoff runs ever," much like how we look at the 2014 Spurs.