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Well "Sanna" and "Form" aren't Japanese, but the sentence structure is. It'd apply to the same rules as a Japanese sentence since "Masaka... kore wa... DLTMS0 no... SANNA FORM!?", where Sanna means true or "shin", follows and relies on the Japanese possessive verb, which rightly comes after the subject. Plus it's not uncommon words from other languages to be employed in Japanese sentences. Heck, it's not even uncommon to hear people just outright say "True Form".
Though I guess "da" is the more popular way to end a sentence about one's true form. Though, thinking about it now, I guess it's not really "required", since the subject, possessive, and predicate are stated in succession, so it'd mostly be for the sake of grammar, but from a logical standpoint it'd mostly be superfluous.