Re: Intriguing....
You can already get NVME SSD drives that are RAM DIMM sticks. The ones I've been presented about actually encrypt the content in hardware as well.
Linux already has some support for this depending what you want to do.
They can be mounted either as volatile RAM sticks (actually persistent, but if you reboot it forgets the previous encryption key, effectively wiping it), or be exposed as a disk that is persistent across reboots (a persistent ram-disks so to speak).
The biggest question is what the write endurance is. Current SSDs biggest limitation is the fact the cells stop working over so many writes, where as with RAM applications assume they can write an infinite amount of time. A naive global replacement of NVRAM with nvme storage would soon cause the nvme cells to be worn out. Hopefully this technology could be a complete replacement.
Even then there is a useful distinction between persistent and non-persistent storage of content. Linkers may modify the in-memory image of the application to insert references etc as appropriate, these shouldn't be written onto the persistent copy of the application as they may not be valid the next time it starts.
An os and applications designed for persistent memory would be an interesting evolution, potentially it would allow 'instant' on machines as the state would automatically be preserved at power off (assuming all components support it).