If you had searched for FIDO2 then you get clear answers already 
FIDO U2F != FIDO2 !!!
Would be nice to have it already but FIDO/FIDO2 are totally different protocols so I read in this forum/other blogs.
Nitrokey sponsored https://solokeys.com/ project and would offer this key also directly; last answer was in this thread:
Nov 18th, 2018
Yes. No specific time frame yet, release expected within next year.
… so maybe end of this year or next year we could expect the new NitroKeys with FIDO2 support (and myself I prefer also with NFC which helps to authenticate also for mobile devices much easier)^^
And even Yubikeys can’t be upgraded and for FIDO2 they have created new devices as written in Internet Security and Company Blog | Yubico