"Not very rational - it's hard to think where else"

Jack has already given a few examples

"concerts in museums, churches, village halls, etc.; singarounds, sessions, grass-roots festivals like ours, taking the music into other areas like schools."

but there are more.

There will always be a place for people gathering together to sing and play although the traditional folk club format of a "booked guest" along with resident floor spots may or not persist.
However, the more informal arrangements will and also small concerts in village halls, arts centres and so on will continue. Of course, these won't soley focus on folk concerts but they will likely always be part of the local programme.

I should also say that the term "folk club" these days covers a multitude of sins. It can be anything from a a slightly more organised session or singaround to an actual concert. In many cases, regulars and members don't get a chance to participate and the support spots are "hand picked" or are visiting acts who wish to gain some extra exposure and volunteer to play.
Also, the music and song may or may not be traditional or even "folky" at all. I'm not saying if this is good or bad but just how things are.

Of course, there are all sorts or arrangements in between but not all folk clubs match the "ideal" which Jim and some others advocate.