This PDF you linked is a bit... "too much technical talk"... but from what I get they're describing this:
https://en.wikipedia.org/wiki/3D_XPoint which is around some time now (the PDF you shared is from a year ago).
I know Intel is using this technology but it's veeeery expensive and I can't see it being used for mining anytime soon. I didn't know Micron has something similar too though, thanks for that!

In any case, this is not an FPGA-specific feature. It's a technology; and since Micron is in collaboration with Nvidia, if this technology becomes mainstream then expect to see this kind of memory implemented it in RTX 2180ti or something.
HMC lost it's battle to HBM2. Micron discontinued the HMC as far as I know. HMC isn't the best for mining but isn't the worst either. Last I checked the older model HMC stock was about $500 a unit. If those could be picked up for $50 a unit it would be worth it. The older micron HMC is only using 16Gbit/s per pin pair - With the newer communications methods it's possible to get 4x that bandwidth per pin-pair (we'd be talking 1Tbit/s bandwidth instead of 250Gbit/s bandwidth). If they made a new version of the HMC using the updated communications methods / protocols and the device was relatively low cost for 4-8GByte units ($250) -- We'd have something that was really interesting to add on the FPGA.