TBH I do wonder what Micron's plans are for XPoint. I suspect that Intel wants to go more down the DRAM route with Optane, which could be a reason behind their split with Micron for 3rd Generation Optane.
It is strange that XPoint isn't in any Micron SSDs, TBH I would love to see a Crucial drive make use of an Optane Cache.
Optane would just be a more expensive SLC alternative. Albeit still faster and lower latency. Not sure if it would really help the super fast NVMe drives.