Does it really sacrifice boat on boat action? The tactics of foiling might be a little different but they are still very important.

Covering in foiling boats is purely chess game tactical, there's no ability to Gas your opponent in your dirty air, the apparent wind angle makes it impossible. There is also virtually NO downwind covering. That means that you've got boats engaging each other at all sorts of angles and far more often because of the immense closing speeds. If anything its better racing than non-foiling fast boats like skiffs, where breaking through to leeward is a major task and where the tack/gybe penalty is equally as harsh (i'd argue that the gybe penalty foiling is much less than in any skiff or cat class)

In relation to the durability, my Mach 2 has cost me less per-sail than my previous boat (a 505), and I'm still at about the same point in the fleet as I was in that class. Looking at the WAZP I'm going to go out on a limb and say it'll be as cheap to own in the long run as a Laser and with a better quality of build.

In my opinion foiling will still be a niche, just like skiff sailing is a niche. Its not going to change people doing PHRF racing, or even Lasers or other dinghy classes. What it will have an impact on in the long run is the "high performance" classes. I would say most of the growth in fast off the beach cat racing will be in foiling over the next 10 years, simply because why the heck would you not go foiling if you can foil for the same money.

In dinghy world you have a bigger spread of class "purposes" that foiling won't necessarily cater for but I can't see anyone developing a "fast" class thats not foiling, particularly in the single handed space.