I disagree.
As with all new sports, with crossover area/fun/conditions - we always see the following:
Because it is new, it is exiting for most of us.
Then there will always be a few saying "I will never do that"
And most will eat their words later, apart from those who lives a bad surf life because they stick to their principle, and keep on riding "the way they were" as dinosaurs
Also, media and brands will expose a new trend hugely.
Third, most surfers will stick to one discipline, for obvious reasons - so those changing to wingfoil will of course lack from kitefoil now - the overall "mass" is still at least the same, actually increased, as new will enter the sport also.
Must say, I can not see why kiteracing would dissapear - as still by far the fastest on the water, when you look away from million dollar crafts like AC72 in some conditions.
For those doing a bit of everything, you can easily see it is very different sports, meaning:
Kitefoil a lot faster to rig and pack and transport (smaller and lighter).
Kitefoil works amazing in a lot less wind.
Kitefoil works great in waves, also steep ones close to the coast.
Wingfoil can be used better than a kite in some conditions like lakes and similar.
Wingfoil can be a good workout (for some this can be both an advantage or the opposite ha haa).
Wingfoil in waves feels great if you get it right, and "far out" swells can even be used.
Wingfoil deliver a new "free" feel, and you can learn many new tricks.
Kitewave works in higher winds and and using the edges and fins gives you clean carves and a nice direct feel to the water.
Kitewave gives you the "slashy" spray feel when riding DTL hitting the lip again and again, nothing can match this.
KiteTT works in higher winds, and you can do crazy freestyle tricks.
KiteTT will give you the ability to jump crazy high, or do megaloops.
Just see when kitesurf appeared, in the windsurfing scene - at first many said "No way I will never do that".
Then years later, some said "Windsurf will die" (because of kitesurf getting huge).
And what happened?
Well, many moved to kitesurf, a few moved back - and today both windsurf and kitesurf co-exist happily together and none of them dropping towards extinction.
Foil or no foil, in both sports - loads of action and riders in all disciplines.
I think we will see the same with wingfoil - many moving to wing from kitefoil, a few going back again - but all in all a good expansion of our water life, new riders appearing, but all disciplines will still be alive and well, is my take on this.
Peter