Please remember that TRIM is one solution, and Apple makes the whole widget. Which is to say, Apple can make their own SSDs (or set the specs for toshiba or whoever provides the modules)
and put whatever support into the OS they need.
TRIM, like all such standards, is a compromise born out of the need for different parties (namely OS makers and hardware makers who have different priorities) to agree on a common solution.
Apple doesn't need to make such a compromise, and can thus produce a better solution. I'm not saying they will, they may not consider the issue sufficient for the effort required and may simply support TRIM, or they may decide that TRIM is the best practical solution for them.
But in my experience watching Apple for a couple decades, them "doing nothing" and it seemingly being well past the time they should have done something, usually means that they are working on what they consider to be a much better solution, and it isn't yet ready.
I think there's a lot of room for innovation in this fundamental shift from hard drives to SSDs.