I may or may not be representative of what's going on right now in the "aftermarket".
I have a 2010 Mk2 Cotic Soul as my MTB and a 2012 Cotic X as my roadie / workhorse.
Three months ago, I needed some new forks for my Soul. I surveyed the market and found that most forks were available only with a taper steerer. I found that the Mk3 Soul had now gained a taper steerer tube and wider seatpost. The cost of new forks, Soul Mk3 and seatpost was well over a grand; for a bike with little discernable differences to my current Mk2 Soul.
This prompted me to look into a Solaris, which would require new forks, seatpost and wheels in addition to the frame itself. While this option would at least give me something "different", the cost of this little lot would have been over £1.5k for my preferred spec... before I even started thinking about different tyres, bars, chainset and cassette setups.
Both options were clearly an alarming pecuniary prospect - and then there was the uncertainty of 650b on the horizon.
I then took another look at what was available for my current Soul... Okay, so the Mk2 Soul doesn't allow for taper steerers, but there's nothing else really to write home about that's better on the Mk3.
I then found some totally bargainous Fox 32 120 RLC QR15 forks *with straight steerer* to plug into my existing Soul. The beauty of Fox forks is that the steerer can be changed to a taper if I want to in due course. I also committed myself to a respray of the Soul once the summer season is over. Hey presto - a fully modernised classic is re-born.
I didn't get around to answering the 29 / 27.5 / 26 dilemma, but I did at least sidestep the question for the time being.
The net result is that the bike industry has missed out on at least some of my spending for the time being. I'm probably also a better person.