It is permanent without more Tesla Board action. The Tesla Board could decide at any time to do more splits or reverse splits. Reverse splits are unlikely. Splitting again once price get to the $2,500 range is probably more likely than not since it worked pretty well last time.
Once TSLA gets admitted to the S&P 500, I wouldn't be surprised if the next split is designed to take it under $200 to make it more acceptable for the price weighted Dow Jones Industrial Average.