Successful as in everyone's going to want to ride it. There's going to be a ton of interest in a new experience especially considering that it's based on one of the most popular Disney movies (not to mention that it's one of the very few rides in World Showcase). Even the people that are against it will probably ride it unless they are completely and unreasonably stubborn lol.
None of those are valid enough reasons to shoehorn Frozen into Maelstrom.
However, they ARE valid reasons as to why Frozen deserves its own attraction, in Fantasyland.