So far, all ‘new’ WiFi standards have been backwards compatible, probably due to the preponderance of existing items that use that format.
Realistically, WiFi standards aren’t changing on a particularly fast timetable. WiFi 7 should lock in standards this year. The next version may be in 2028, but there was an 8 year run going from 5-6.
The truth is that you will have components fail or other technical constraints come into play long before the wireless radios.
I think we also have to be realistic that these are very complex technical devices that include speakers. They aren’t going to have the live spans of some older speakers.
Looks like WiFi B and G are still supported, WEP is gone though and WPA is the minimum.
WPA is about a 2003 standard while WiFi B is about 2007.
I wouldn't worry much.
https://support.sonos.com/en-us/article/supported-wifi-modes-and-security-standards-for-sonos-products