I have been following the developments regarding this technology regarding cruising boats. In fact it is not a new thing, the French have toyed with it on the 80s in what concerns offshore racing boats but the concept never proved to have reliability and enough efficiency.
It seems to me things are changing fast and the ones that seem to be leading the ball in what concerns practicability, costs and a possible utilization on cruising boats are One sails, the Italian sail company. In fact they believe that in 15 years almost all boats will have some kind of a wing sail.
I have saw their first video (that I will re-post at the bottom) but only recently I saw one with a comparison on the water between two identical boats, one with wing sail the other with conventional high quality sails and the results are conclusive even if the sail is still in development:
Aile souple : la voile du futur ?
The boats are Seascape 18 and we can see that the wing boat is not only faster as it can point 5º better upwind and sail downwind at a bigger angle.
The wing can be reefed and I believe that this type of soft sail wings will not take long to be available, first on racers and after in performance cruisers.
Here a previous movie with that sail on a previous phase of development.
and they are not the only ones working on it: