acorn will no doubt give you chapter and verse on this, especially backwards compatibility

but I will just say that actually, xara/magix are not the only company that 'allow you to use a later version than the one you actually paid for whilst you are paying for something else'

In the case of toonboom, for example, that something else would be a support contract

In xara/magix' case it is an 'update service' - most here would beef that in magix case the updates are few and far between and given the small print re the actual program updates it would be better called something else 'added value service' maybe, I dunno...