I predict more and more OEM-sourced parts on bikes (and with that will come proprietary designs). It's already happening to some extent, but I think that in the future we (consumers will not have the ability to upgrade things like stems, seat posts, seats or handlebars unless it's a design made specifically for that bike (and therefore licensed by that manufacturer). These designs will continue to become more integrated into the frame and overall bike design.

This might extend to electronics as well. Rather than an aftermarket Garmin or Wahoo head unit attached to handlebars, bikes might come with an integrated screen built into the handlebar/stem design that connects to a smartphone and built-in wheel/cadence/power sensors on the bike.

I do also wonder if the era of being able to easily customize a bike by selecting a frameset, wheels, components, finishing kit, seat and handlebars all from various manufacturers may eventually come to an end, especially the designs of these parts become more integrated into the frame design. It's getting increasingly hard to find top tier bikes with standard seat posts, for instance. Companies like Specialized have already done this with wheels, seats, etc - will they take it a step further and develop their own S-works drivetrains? Will companies like this always rely on SRAM and Shimano to provide parts for their flagship products?