There's only a year's difference in Maddie and Mackenzie's ages? I would have guessed more, given how they're portrayed on the show. I wonder how soon it will be before Mackenzie and Maddie will have to compete in the same division with one another when it comes to solo work? I would think that could be difficult for them, as sisters, to have to do that, though, in general, I am impressed by how well the girls handle their relationships with one another, given all the chaos that surrounds them.
I also wonder how much longer some of the mothers/kids will continue on with the show. Holly seems a little more grounded than the other moms and to want her daughter to have a solid education beyond dance, which is understandable, given her background as a principal and given how short even a successful dancer's career can be. In two years or so, Nia will be ready for high school. Will she want her to continue to be spending so much time on the show if it distracts from other opportunities? Personally, since Holly has recently mentioned that Nia is interested in other aspects of performing too, I think she might find a more general theatre experience valuable. Her dance/movement ability would certainly still be helpful there, especially in musicals, but she'd be able to explore other avenues of performance too.