The issue with Kitty is that its graphics protocol is not widespread yet, so some of the CLI/terminal programs OP uses that can do graphics output may only support sixel. But yea, personally looking forward to Foot terminal implementing one of the fancier graphics protocols, even if it feels more like a toy at the moment (until they are used more). But seriously running the notcurses[0] graphics test with a terminal supporting the kitty graphics protocol is sex, just like the program itself says.
It's not! Gnuplot in the terminal open many new use cases, such as examining data on remote hosts with scripts without even bothering to scp the data first.
As for kitty format, adding support in sixel-tmux is planned, but you are welcome to write a patch if you want it sooner!
Imagine sixel-tmux as some middleware, because it is totally possible to intercept sixel sequences and rewrite them on the fly into something more palatable to kitty or iTerm.
This way, even if gnuplot doesn't support kitty, you could still view the results. If it's done well enough, you may not even perceive the difference!
That's the direction I want to follow, so that users can take any software and play with it on their terminal regardless of the underlying format.
A matplotlib backend isn't even needed, just a cool piece of info, it's possible to extend ipython and/or jupyter console to display pngs and svgs with sixels (and/or kitty graphics, dynamically). I have code lying around for this.
I have to check the current state of rstudio/ipython console support with sixels: doing everything from the terminal is a luxury I want in 2021, especially now that hidpi/4k screens are becoming mainstream :)
Last time I tried in uni on a "new" Thinkpad R52 (well, new for me as it wall already over 10 years old, but it had such a glorious 1400x1050 display!) quite a few things were missing.
You misunderstood me, I was saying Kitty graphics protocol feels more like a toy in how well it can produce graphics (GIFs, videos, etc). Sixel is more common in actual use cases (at the moment). But, take notcurse's graphics demo for example, using the kitty backend, it's very unreal terminal experience. But once Kitty's graphics protocol has more widespread support, for example in graphing tools, it'll be just as useful as Sixel :)
[0] https://github.com/dankamongmen/notcurses