I think rim brake bicycle will have its market share, until they stop producing rim brake wheels.. even for little kids bikes.
If you already have good rim brake wheelsets and feel no need for extended braking performance that require disc brakes, then stay with rim brake bikes.
For now you have more choices in cheap carbon frame with rim brake vs disc brake, try one see if you like the ride of cheap carbon frame; when you're ready to move on to disc brake, by then maybe cheap carbon disc frame would also become more popular to have more choices.
[u]Here's an interesting frame:
Disc & rim brake compatible, QR & Thru-axle compatible.
