To return to the OPs question.
I don't see that a Third revival (whatever that may be) is actually happening. Certainly any Americana influence isn't very evident in the UK.
What is happening is that a lot of young people are finding the music for themselves.
Quite ofen by associating with other young people, a lot of whom are the children of established artists, and have therefore been surrounded by the music all their lives.
Try and imagine Eliza Carthys upbringing. Not only parents who performed, but an aunt and uncle too..(not to mention probably lots of other singers and musicians popping by and staying over whilst on tour.
Hardly surprising that the music would just seep in, by Osmosis.
Also, Degree courses like Newcastle, are producing a whole raft of new musicians and singers.
So, you could call it a revival, to me it's more of a continuation. The only change is the decreasing relevance of what we would call the "Folk Club"
Pre the internet era, The FC was really the only place to find this kind of music.
But nowadays, access is available everywhere. Yes of course some clubs survive, and some are brilliant at it, but the new generation seem to doing it another way.

So, not dying.....Just changing, as always.