Straight from the Avast Support:
So, they're gonna keep rolling out definitions updates for 18.x so Windows XP computers are still gonna be updated, but if something breaks, they're not gonna fix it or release any new update from now on.
In theory, given that they won't be rolling out updates, they also won't break stuff (in theory), so we *should* be fine (emphasis on "should").
The only positive thing in all this is that they at least fixed the high CPU usage issue, so normal bare metal systems won't have issues:
The reason why I mentioned "bare metal" systems specifically is that there's still an issue with VBoxTray.exe when the new guest additions are installed, but that one will never be fixed. The hope is that this will be addressed by Oracle as it seems to have something to do with Avast's behavior shield which, for some reason, seems to be going berserk with the new guest additions but was totally cool with the old ones. Nonetheless, as far as Avast is concerned, the only thing we know for sure now is that:
1) They will not release any new program update (so any new bug will never be addressed/fixed)
2) They will still keep releasing definitions updates
3) They won't help anyone with XP if you try to go through their support, regardless on whether you have a paid subscription or not
It's not quite the end of the road, but it feels like we're slowly getting there as we're approaching 2027.