I would seriously doubt anyone here could answer that question.
But you are surely not alone in the waiting.
Given Intel's conservative and careful testing and validation process (which is a very good thing) of their hardware and software, which IMO is not driven by hard release dates, I doubt very highly a specific date will be provided. Frankly, I was surprised Intel mentioned the support of TRIM in RAID 0 in a future release of IRST. I would not be surprised if that statement in the IRST Release Notes was not meant to be there, and its inclusion was a mistake. Given the high profile nature of this feature in the PC enthusiast community, I'm sure Intel is being extra careful that it works correctly.
As with the 520 SSD, IRST with TRIM support in RAID 0 will be released when it is ready.