If it’s like other Clockwork hardware (take the Gameshell, for instance), eventually people will move on and no active development or projects will be appearing, but we don’t seem to be anywhere near that point yet, thankfully!
What comes on the SD card with the device only works with the Pico. The Pico 2W can either use the PicoMite build for Pico2 or the Webmite build for Pico2. You won’t be able to access wifi features with the PicoMite build, but you’ll have a bit more memory free, and some other PicoMite features. I don’t think there’s a good list of the differences between versions, but if you don’t mind sifting through a lot of information it’s in the PicoMite manual. There’s no updated manual for 6.00.02 builds yet, but I think most, if not all of the functionality is backwards compatible with that release, and it’s just some extra commands, maybe some extra parameters and options, and some bugfixes that come with 6.00.02. The changes are listed in all the (many) posts on TheBackShed, but hopefully the docs will be updated when the new version is officially released. Right now it’s just RCs, but people (including me, mostly out of curiosity) seem to want the latest so it’s there at the link below. 
I haven’t kept up with the MicroPython development, but last I looked it was quite active. Documentation was slim, and I’d recommend reading everything you can about it on the forums here, since it sounded like some of the information posted on teh github was incorrect and people had to do things differently to get it fully working, but it was discussed in the forums.
There are at least 3 different version, I think. The first was for an ESP32 based WalnutPi, but zenodante’s seemed to replace it with a more robust (but maybe not documented well?) version. And Laika adapted it or created a new one too, I think?
Best to ready everything at these two threads to catch up. I’d have to do the same as I have no idea what the current “best procedure” is to install MicroPython on a Pico2 with the PicoCalc. I’m guessing it’s zenodante’s, but I could be wrong.
Kinda sucks that the only way to find out about what’s going on is to sift through months of posts, but that’s kind of how things have always worked around here. 
See the link I posted in the message above this. It’s my own fork of the official PicoMite repo. Originally it just included the adaptations made by guu for the PicoCalc hardware (mostly display and keyboard), but it’s seen a number of bugfixes, rewrites, and even benefitted from a compelte display rewrite that was done from teh official sources to support a very similar display to ours. Keyboard stuff was a bit of a mess in the old version too. And the version that shipped on the SD was for a much older version of PicoMite, without any options for Webmite or wifi access.
Forth was already metnioned above, and while i haven’t tried it myself, it seems like they’ve been making a lot of progress. The uLisp folks have made considerable progress too, and I think it may be the first “officially supported port” project for the PicoCalc as it sounded like the uLisp maintainers brought the changes into their own project. I’m not a Lisp enthusiast though, so can’t really comment on it beyond knowing that it exists and has made progress. 
I think those are the main languages that people have worked on for the PicoCalc so far. The other big thing (which I still need to dig into more for PicoMite) is the SD Bootloader to avoid the need to flash firmware as often. Currently, it’s only usable if the firmware is rebuilt to support it. Guu posted a version that incorporates a PicoMite build and the Bootloader into one firmware, but it’s only for the Pico and only for that specific version of the code. I’m hoping to dig into it again at some point and replicate that for the Pico2 and also get it building in a way that can be synced and kept up to date with changes in teh mainline PicoMite code. I’m also considering breaking it out compeltely (as teh bootloader was originally intended) and using the work guu has done to have “bootloader friendly” builds for the PicoMite variations. Thing is, the SD_Boot developer already has plans to enhance it so it coudl theoretically use firmware as it is, without having to be rebuilt. If that happens, then all this extra work will be unnecessary. So partly this is an issue of figuring out where it makes sense to spend time.
I’ve got a few other things planned for the PicoMite build though, like setting the display brightness from mmBASIC, and cleaning up the existing code that allows for setting the keyboard backlight, among other things.
It’s also worth noting there are developers who have been using the PicoCalc as an arduino platform, and git has several examples of working drivers for the PicoCalc hardware, as different people ahve independently figured out how to do it and built their own libraries. It’s unclear which of those is the “best”, but there’s plenty of stuff to sift through and adapt or get ideas from. I’d recommend doing a search on github for “picocalc” and plenty of stuff will pop up. I’m not sure what that “picocalc sd formatter” thing is, but it seems like some kind of AI generated garbage and considering the useless and frequent updates to it, it could be malware.
If you’re interested in using a different module, the Luckfox Lyra is an impressive option instead of the Pico2w. It can run actual Linux, has considerably more memory and processor power, but still fits in the Pico module slot. The downsides are some soldering is required to get sound working, and you won’t be able to benefit from any of the other software/language work being done for the PicoCalc, but since it’s Linux you can pretty much build and run whatever you want, assuming it can run via a Linux terminal, and doesn’t do anything too fancy in terms of graphics, though SDL has been supported so things like Doom and even retroarch can run, though they have limited performance.
Sorry for the long reply, but that was my attempt to try to summarize things that have been happening around here. Hopefully some of it helps!