The plant has no true "need" for a dormancy, but is more than capable of going dormant if conditions arise (and capensis might not be the best example of a "tropical" species, as it grows in a Mediterranean/Maritime temperate region that does see frost and occasional snow and so it has means of enduring such conditions in a semi-dormant manner in some forms). Crosses like these already exist in abundance (the one you mention is unofficially and technically improperly named D. x "rotensis"), and this habit is seen in most of them, like new versions of D. x tokaiensis var. hygaensis, D. x belezeana ("eloisiana") made with the tropical forms of intermedia, intermedia x madagascariensis even, etc.