I think the marketing men's perception of 26" is skewed. There is no reason for 26" to be a "rugged" size, it's just a size. You can get 26" tyres down to about 1" (28mm) for roadifying MTBs. Personally I would like to see 650C folded in to 26(MTB) so, just like in 700c, you have a whole spectrum of widths for one diameter rim. You can have rugged rims and lightweight rims, racing, touring, commuting and off-road, all in one 26" diameter.

There seems to be a real gap in the market for lightweight commuter/touring bikes using a 26" rim capable of taking medium tyres (28/32mm). Who needs this? Only all the small people in the world.

Schwalbe ballon tyres such as Big Apple and Kojak are taking the role of French style 650B for urban riding. I ride Big Apples and they are really comfortable but efficient. They are still a niche product rather than mainstream.
650B revival is a bit odd but it is a boutique size for people who like to be different. Its a nice size but before we make 650B mainstream, I would prefer to see lightweight 26" (MTB) expanded.