"Disney Princesses" was the article that started this derail, not just "any random selection of Disney-owned characters." The Princesses are a bit more conceptually relevant to each other, and they've been a marketing thing for years now. As I said earlier, it's already been done quite well on TV. (Making it unlikely they'd do it as a movie, I think.)
The main issue is whether the creators have the chops to pull it off, and whether the backers are motivated by making a quality product or by greed. Hollywood generally works on the basis of "Give me something just like that -- but different!" So, pretty much any project that bears any resemblance to another needs to be taken with a grain of salt.
I was doubtful about both Once Upon a Time and Grimm starting at the same time, because I figured one was going to be a ripoff of the other. Turned out both were really fun, and it wasn't a concern. But that copycat tendency always makes me wonder.