Kitefoil: seems to have plateau'd.
Windfoil: all of a sudden, 4-5 of the local windsurfer community took it up last year (they travel in packs). And suddenly they are actually stoked about sub 25kt conditions again, even saying things like "I wish it would get less windy so I can foil". LOL
SUPfoil: just me and a buddy last year, now another 2-3 starting, another half dozen just about there. The learning curve is fairly steep; we were a really bad advertisement, "more fun than it looks, trust me!". Now we are intermediates and getting some solid rides, I anticipate more people are seeing the potential.
SurfFoil: no one yet, but a few people nibbling at the fringe. I plan to progress to that, once SUPFoil "mastered". I suspect that's where we may see some lookie-loo's become doers, as the SUPfoilers tend to be just standing there riding along (similar to SUP riders in general), whereas the SurfFoilers are ripping! Going fast, quick turns, in the critical sections, like surfing on speed. I look forward to giving it a shot.
[Slappy: if you ever get to south VI, hit me up for a demo ... just like the pusher, first one's free