I'm not a System76 developer, but I'm excited about the new Rust based COSMIC desktop environment and like to share progress as I see it. Even though it's still pre-alpha software I think it's usable as a casual desktop that does some browsing, editing and communication type tasks. A little knowledge of controlling the system via command-line is helpful when currently playing in COSMIC. For example, you may have difficulty setting up a network and VPN, but command-line works fine for that. Just nmcli is enough. Maybe preparing some scripts beforehand will be of benefit as COSMIC utilizes your .bashrc and/or .zshrc. Additionally, it uses auto-suggestions, auto-completions and autojump so it makes living in the terminal a breeze. Having said, most Flatpaks and Nautilus are working fine. I think some Flatpaks still don't like Wayland much regardless of DE. Tiling works great and stacking was introduced recently. Resize is a fresh inclusion and is working well too.
Above is a new screen which shows a neofetch and that I've been on for three and a half hours. In that time htop shows I'm clicking along at about 2GB memory. That includes cmus and OBS utilizing Pipewire. OBS is running on another monitor along with Nautilus and Image Viewer. So a nice load. Although I can do a nice screenshot with OBS, the desktop bogs down if I try to record or stream. It spikes about 3.6GB and the mouse is close to unresponsive, but works if you're patient. You'll notice that the "niceness" set by system76-scheduler is working properly too.
What I wanted to spotlight in this screen was the diacritics seen in cmus player. These are a result of cosmic-text, a brilliant piece of software written in Rust from scratch by Jeremy of System76. It handles text shaping, rendering and layout. The diacritics you see are French, Icelandic, Tunisian and German. The reason I wanted to spotlight this is that critics of COSMIC DE said it would take three YEARS to achieve just this one thing. Jeremy had it working in three weeks. The rate of development for COSMIC is amazing fast. There's a way to go, but it's looking so good.
Will you be able to upgrade from an existing install or will it need to be fresh?
The technical answer is that COSMIC is a desktop environment, and like any other desktop environment you can install it on top any Linux distribution that supports it. Meaning it should be technically possible to install on an existing 22.04, or maybe 24.04 Pop!_OS. But here's the tricky bit, and nothing is concrete yet. COSMIC DE might be getting released on a new Pop-core which will not be what already exists. In that scenario a fresh installation would likely be necessary. So to answer your question - I'm not sure how that will roll out just now.
I will say this. After using and watching Pop!_OS development for five years now, whatever System76 release will be awesome. It simply has to be as they're a hardware sales company and need a stable, secure and functional OEM operating system.