If I could buy a 5k (retina) 120hz 27" monitor that would be endgame for me, I believe this finally has the bandwidth for that.
The issue is more likely to be availability, and marketability.
In general the demand for high refresh rates on desktop displays is driven by gamers, far more so than resolution - it's pointless having a 5K or 6K display if your GPU can only render the game in a playable fashion at 1440P or whatever. This demographic is well known to sacrifice resolution for higher refresh rates. I guess a low detail image that animates smoothly is preferable to a high detail image that is jerky or looks like a slide show.
A large part of the buying market for high resolution displays (particularly above 4K in the 27-36" range) is going to non-gaming users, who are doing regular desktop work where 60Hz is likely to be fine. Most people aren't going to be able to type or draw or do much else productive fast enough to "defeat" 60Hz for practical uses.
I don't think it's a coincidence that Dell, ASUS, Samsung, LG and BenQ all have high-end displays shipping or announced, that explicitly mention support for macOS, and just happen to use a PPI that suits macOS' scaling "@2x" scaling mode perfectly.
Nor do I think it's a coincidence that the 5K@60Hz spec they mostly support is viable on Macs as old as the 2016 MBP15, from 8 years ago. Heck even a 2018 Mac mini with just an iGPU will do 5K@60Hz.
I'm not saying no manufacturers will support higher refresh rates, but realistically I think you're looking at a product that would be a niche within a niche. It's only recently that most of the above manufacturers have (re)entered the ~200PPI display market, it's going to take a while before there's enough potential customers for what you're talking about.
And so it's odd you think they wouldn't bring it to the external displays. Especially when going back to 60Hz is definitely noticeable whilst doing desktop work i.e. lots of web page/document scrolling.
With gaming monitors now doing ludicrous things like 1440p@480fps, I don't think 5k@120fps would even be difficult for manufacturers.
Stuffing everything over a DP 2.0 connection may be difficult, though, but DP 2.1 has been with us for a while now. 5k at 195fps (159fps with HDR enabled) can already be achieved with a standard DP 2.1 port.
When it comes to displays, I think we're currently limited by GPUs rather than Displays. Nvidia's 40 series GPUs only come with DP 1.4, for instance. Until 2.1(b) gains wide support, it doesn't make any sense to build monitors that rely on it to do their job well.
I didn't say it's difficult technically, I said it's about whether they think there is a market for this product.
I too get 7680x2160x120Hz via TB4
The recently-available Asus PA27JCV is 27" 5K, but unfortunately not 120Hz:
* https://9to5mac.com/2024/12/26/asus-proart-display-5k-review...
Currently selling for US$ 800 (less expensive than the Apple Studio Display):
* https://www.bhphotovideo.com/c/product/1850479-REG/asus_pa27...
I'm considering it for a replacement for my aging 27" 5k iMac (paired with a Mac mini I guess).
LG recently teased a 32" 6K with TB5:
* https://www.macrumors.com/2025/01/07/lg-unveils-ultrafine-6k...