What's odd is that the original 500 already had an unpopulated M.2 slot, so they considered it a year ago but backed out for whatever reason.
So I don't think they "backed out" rather just didn't have the 500+ ready to launch yet.
According to an interview on the Pi blog[1], it was "years", with prototypes being built through 2023.
I know the design lifecycle for a product like this is in the 3-5 year range, and adding on a custom mechanical keyboard in a mass-market product like this is a tall order.
Honestly I'm not put off by the $200 price tag. If you use one in person (like at a Micro Center here in the US), you'll feel it's a decent midrange mechanical keyboard. It won't compete on the high end (IMO $200+), but to strap that onto a decent low-end PC in a fanless design isn't cheap, even at the scales Raspberry Pi operates.
They have some margin, for sure, but that's also how they turn profit, which is especially useful since then went public.
At least they're still putting out products like this, that don't really have any industrial/commercial appeal, compared to specialized compute modules for individual customers[2].
[1] https://www.raspberrypi.com/news/meet-the-engineers-behind-r...
[2] https://www.cnx-software.com/2025/09/23/raspberry-pi-cm0-cas...
Even low-midend mech keyboard like attackshark x75 will be better
Even the connection to the new keyboard was already present on the 500 even though it used another connector than the 500+