Predicting the future in the bike business is an exercise fraught with peril. Take for example, my pal Bill, a former bike shop owner and my former boss, who saw mountain bikes coming out in the 80s and predicted that they would be the end of his business, since they were "so durable that they would never need repair." (For the record, Bill is now out of the business by choice, not because he was driven out by those indestructable mountain bikes.)
I wasn't in the business when MTBs hit, but if a customized Delorean had pulled up to Bill's shop in 1999 with a message from 2017 that the 26" wheel (a.k.a. 559mm bead-seat-diameter) was all but gone, replaced by some obscure French size we probably didn't have in stock, I would have laughed that fool right out of the parking lot. Yet, here we are in 2017, and see how many 26"-wheeled bikes you can find in the catalogs of any of the big players. They've all been pushed aside for 27.5", a.k.a. 584mm bead-seat-diameter, a.k.a. the obscure French 650B.
Still, with all that evidence of past failures piled up against me, and my own Luddite retrogrouch tendencies crying "say it ain't so!", I'm going to step out onto a dried, cracking limb and say that 2017 will be remembered as the year that the invasive species known as the disc brake finally sucked up all the oxygen, leaving nothing for rim brakes.
Sure, the pro peloton hasn't embraced them (yet). But that (finally) doesn't matter. We're in a marketing moment where new riders just aren't excited about skinny dudes on skinny tires in tight shorts (not that there's anything WRONG with that). For all my grumbling about the hooey around gravel bikes, the industry push these days is away from one-trick race machines towards all-surface, all-purpose bikes (you could say that Rivendell's vindication finally came). For once, a bike can still sell even if it doesn't look like the one some doped-up freak with 2% body fat rode real fast around France for three weeks. And for better or worse, the big players (and fashion police) have decided that those all-surface bikes must be disc-equipped.
Once those high-end/enthusiast dominoes have fallen (and you don't have to spend much time looking around your local bike shop or trail to see that they have), it's just a matter of time before rim brakes go extinct all the way down to the Wal-Mart level. The message that discs are better in wet, mud, and snow is pervasive... even though a huge percentage of riders won't go out in those conditions anyway, and would be just as well served by a good rim brake. The stores are going to love it, because the ability to brake no longer relies on the ability to keep a wheel trued. And the manufacturers are going to love it because they only have to weld on a couple disc tabs per frame rather than four precisely-aligned cantilever posts.
Fear not, those who come here for retro-grouch grumbling. The Cycle World Headquarters remains a disc-free zone, mainly because I'm not the least bit dissatisfied with the cantilevers and V-brakes in my fleet -- they even work on (gasp!) gravel. (It also helps that switching brake paradigms at this point would be a costly and time-consuming endeavor, and I'm a cheap, lazy man.) Still, even though I've held out vain hope that discs would be the Biopace chainrings or chainstay-mounted U-brakes of the 21st century, I think we're stuck with them.