Whatever his DT will be, you can be sure it will be visually stunning the first moment you burst into Demon form, even better, as they usually announce the arrival of his DT in a cutscene, it might just be amazing to the eye.
I liked his DT in DMC1 more than any other, but I love the Sparda form that is his true Demon form from DMC1, so I think they should try to go on that more than anything.
Dante Sparda, if he aint got a surname due to the fact that his Father was a Demon and didnt need one, I'd just call him Dante Sparda, its only right since he inhereted his Fathers powers and form, why not his First name as in some human cultures.