djb

thats a good question, but I really dont know. Even though I have friends in France, they arent bike people, and I don't keep track of European market.
I suspect however, that 27.5 is getting more common, simply because there are more and more bikes with it.
I do get the logic, 29er stuff was designed because it rolls easier over bumps, and then they figured out that inbetween 700 and 26 is a good compromise, so I'm not even against getting a 27.5 bike at some point.
I suspect also that my 26" designed Surly Troll would work well with 27.5 , within reason of tire size, as the outer diameter of tires I would use could be similarish to the 26 wheel/tires combos I've used. I just mention that without checking the details, thinking of perhaps a future wheelset choice (thinking wider rims that would work with 2.5-2.8" tires better)

I still feel that no matter, gazillions of 26" bikes are going to be around for ages, and good tires will always be able to be sold, so companies should keep making good tires.
We'll see....