Considering they are for cheap (like pre-2020 bluepill prices) on AliExpress, they might become interesting for hobbyist, provided there is decent toolchain support.
And for the new architecture, well, if there runs a proper GNU Toolchain, most will write in C anyways.
For what I can see now, there is upstream newlib, gcc and binutils support.
There is this binary distribution in AUR (
https://aur.archlinux.org/packages/csky-elf-tools-bin/ ) However, that is rather old ( GCC 6 )
I am now trying to compile the current versions of the toolchain by taking the ARM PKGBUILDS and changing the target.
It's building right now, but compiling it all will take some time.
So it seems, what is required to build a binary is covered. What concerns me more is debugging support. I haven't been able to locate any debugging support for the thing. And then the line
Debugging – CH340 via micro USB port
looks scary. It would imply it will be Andruino-style printf debugging, in other words, none.
Looking at the datasheet, there appear to be debugging pins present, without looking at the details, it implies the hardware has proper debugging support, but the software part is missing. There is this package in AUR
https://aur.archlinux.org/packages/csky-debugserver-bin . I haven't looked at it in detail, but it seems to be requiring a debugger manufacturer-specific debugger probe.