SMN is a bit harder to balance for because its regarded as being more technical than the other DPS classes. The DPS gap from min-max DPS is fairly large, I'd imagine since you can have someone at peak performance and then someone who... only knows how to use Ruin / Ruin II..
As such, I expect a lot more thought has to be put into HOW to change SMN versus doing direct potency/TP changes like for DRG/NIN/BLM, etc. I'll need to go through the history, but it would be interesting to see how long the time frame was when S-E said they would begin changing WAR before and then actually enacting their massive WAR overhaul back in the 2.0/2.1 era.
[EDIT] Just going through
dev tracker history with WAR changes being indicated back in October 30th, 2013. A more detailed explanation was given on November 20th, 2013 and the patch went live December 14th, 2013 for the WAR overhaul. Given the potential magnitude of changes needed for SMN, I'm personally not expecting a change until expansion now, but will gladly eat my shoe if that happens to be different.