@opera5, it's fine if Mozilla continues to support W7/8.1, but even if this is the case, users will have to be clear that going online with an outdated OS and without official support is a security risk that gradually increases in time. Apart without a date isn't correct, also Mozilla will end the support in September of 2024. There is no other way to update to Windows 10/11, or, if not possible, to switch to Linux, maybe in Dual Boot, using Win7/8 for offline tasks if needed.
Microsoft ended official support for Windows 7, 8 and 8.1 in January of 2023. Unsupported operating systems receive no security updates and have known exploits. With no official support from Microsoft, maintaining Firefox for obsolete operating systems becomes costly for Mozilla and dangerous for users.
Mozilla is providing critical security updates through the Firefox ESR channel up until the end of ESR version 115, September 2024. After this, no security updates are provided and you are strongly encouraged to move to a supported version of Microsoft Windows.