I always saw Prince Naveen as an ENFP. He's constantly dreaming about the day that he becomes rich, a definite NF trait. He also seems very imaginative to me and not really concerned with what other people (except, of course, Tiana) think, and makes huge and impractical promises to people that, had this not been a Disney movie, he probably wouldn't be able to keep. He's definitely a dreamer, I honestly can't see him as an S.
And I know sensors have a reputation to be a little more shallow, but this is probably a result of him being spoiled and sheltered his entire life. By the end of the movie, he's selflessly giving up his own happiness so Tiana can have her dream.
Besides, if Tiana's an INTJ (and I haven't read what you guys have said about her yet, that's just from my own personal assumption), it works well, because INTJ's and ENFP's match well.