[cflsystems]

As far as I know 5.4.2.x was supposed to have significant changes over 5.4.1.x. If the move now is to 5.5.x I can only assume the changes will be even more drastic and there will be no compatibility between 5.4.x and 5.5.x - while 5.4.1.x and 5.4.2.x would have been compatible to a degree.

It is of no surprise they won't make 5.4.x PHP 8 compatible - there's way too many 3rd party vendor packages to upgrade as well as the core code, modules, etc.

Considering even PHP 7.4.x now gets only security updates and only until the end of this year I would say XC is again very late for the show. By the time they release 5.5.x and it is consider stable it will be 2023 and PHP will be way into the 8.x version.

5.4.1.x is not dead but its safe use pass end of this year is questionable. It can be made PHP 8 compatible the question is why would anyone outside XC do it. Too much work and it has to be packed as its own package, cannot be installed as a module, not to mention licensing issues...
You can also expect with 5.5.x SL will tighten even more the SaaS model.

I think it is save to say XC5 is turning into XC4 - slow but sure decline in user base over few years. Unless SL somehow manages to move its Amazon user base into XC5 based marketplace(s).
The great advantage XC had over competitors for years was its source access and the fact that anyone with knowledge could do anything with the cart to fit any type of business or requirements. SaaS may be great for the owner of the software but it is not so great for the end user, in my opinion.