My confusion re: cessation of direct, non-stop Express SARL service, may stem in part to the fact that it may have been stopped in two stages.
There was direct, non-stop express service between Makkasan and SBIA/BKK, AND direct, non-stop express service between Phaya Thai and SBIA/BKK. So two separate and distinct service schedules.
Track reconfiguration west of Makkasan would address this anomaly and allow for a single service with stops at Makkasan, not sure if that was ever done.
So I think these services stopped at two different times as the rolling stock became impaired. Maybe Makkasan Express service stopped in April, 2014 and Phaya Thai in September, 2014? I assume a read-through of this thread would reveal the details.
I guess they are refurbishing the Express sets as well, but no idea if the Express service will ever be re-started? My guess would be no, and that they'll use Express sets for City Line service, but one never knows with the SRT>