As I understand it the approval of moving the Seattle Sonics to OKC was approved on this very day in 2008 and at the start of the 2008-2009 season they were the Thunder.
Not exactly apples and apples because they were moving cities, but these things can be expedited if it need to be.
It does make you wonder, because that is true about them moving. It would be bad pr for the merchandising sells to announce a plan of rebranding and then it taking NO two years to do it. If the NBA and the two franchises can get this done over the summer it would be awesome. Especially with the energy peaking for this.