Most SSDs use 64-layer NAND and the newer ones use 96 layers. I think you meant 3 levels, i.e., TLC.
I'm sure there will be a trend toward 4TB M.2 now that I have the U.2 drive. I don't think any M.2 can keep up with the sustained writes as well as the U.2 SSDs though. I'm hoping to use whatever 4TB SSDs I have in a new computer which should have several M.2 slots.