Question for the bike guys on here. Im looking to sell my road bike to upgrade to a road bike with disc brakes. I know the market for rim brakes is shrinking quickly, but I feel like there is still a market if I move now, especially with zipps on it.

2018 Cervelo R2, 105, (blue/green color scheme). Purchased new in late summer 2019 and I only have 426 miles on it, most of which was during summer 2020. MSRP was $2300.
Currently has a set of Zipp 404 wheels with brand new freebody and brand new bearings that will be included as well as a set of look keo pedals.

Good rim brakes will throw you over the bars just as quickly as discs and the front wheels don't need as many spokes to transmit the torque.

Have you considered going with a new front fork and just doing a front disc to save on the depreciation hit?

As for value I purchased a used Trek 5500 in 2005 that was ~3 years old with only about 50 miles for about $700. It retailed over $3k when new. Might have been the steal of the century but is an example of how much depreciation you might expect.

personally, i think disc brakes on a road bike, while a nice plus, really aren't needed unless you are truly racing and in a peloton type setting. The caveat would be if you are doing some gravel riding.

Now, disc brakes on my mountain bike are a god send.