It's an interesting topic that's come up a few times over the years. The closest parallel I can see is Hang Gliders. Not dissimilar to two race sails foot to foot. Similar speeds (at least close enough in aerodynamic Reynold numbers terms). Double surface wiped out single surface in competiton overnight. Although single surface remains for lightweight recreation ; but even then there is some DS at the leading edge. Pretty much like a current race sail.
When the wide luff race sails came out some said it was a gimmick, I thought the sock size and shape would mutate into a wing sail. But intensive development but several brands has proven that
1) They do give a (small) performance improvement
2) There is an optimum DS luff size
Exactly why is debatable, but it does seem to be a fact - at least until someone proves otherwise.
Ten years ago a start up in Scotland got as far as taking orders - but didn't get many. Boards magazine did test an early example and said that as a lightwind sail it did have amazing glide thru' the lulls. But commercially a big name brand would have to sell it to convince a sceptical public. Weight and production costs are huge issues.
It was interesting to see a solid wing in the A class cat championships too, against the best in current sail technology. (Their sail weights make formula look lardy). Competitive in it's first version at world level , but didn't make everything else obsolete.
Actually I've just been playing with an 8m Neo foil kite, they're just some much neater than inflatables to me all round. Jumping with these is more an inevitability than a skill ! Will be interesting to see if foil kites find a niche in the new kite course racing. If so we might need some lightweight high twist DS formula sails to avoid being left behind !