http://tvline.com/2016/01/15/so-you-think-you-can-dance-season-13/

"It won’t fundamentally change the show, it will just give it a little bit of spin,” says Fox boss Dana Walden of the potential changes.

There are examples of changes involved in order to gain back increased ratings in Season 13 than in Season 12, besides no more of this "Street vs. Stage" situation:

1.) The age range should shortened a little bit.
2.) Mary Murphy, not only will return as a judge, will more likely replace Jason Derulo, who doesn't talk like real judge not getting his facts maturely polished.
3.) The latin-balloom performances will return after a season off, due to a fast increase amount in season 11, leading to hurried transfer to DWTS.