Outside of Xenoblade, what other Wii games are Nintendo remaking for the New 3DS? I don't think I've heard of any others. If that is the only one, that doesn't mean that if a Galaxy remake were to happen for whatever reason, that it would most likely be for the New 3DS.
I'd much rather see it remade for the Wii U. It would look absolutely gorgeous. Putting it on the 3DS would be doing it a disservice. There's not much of a reason for them to remake it though, since the Wii U can still play it.