According to these leaks, Rockruff's evolved form has four forms, just like the starters'.
Not saying the leak is true, but we also now know for sure that the new faggot in the manga has Rockruff as his main companion. CoroCoro also said that Rockruff has "something special" in common with the starters, whatever the fuck that means.
All of this is leading me to believe that Rockruff is intended to be a sort of extra starter, which hasn't happened since gen 1. So maybe either you'll be able to choose Rockruff as a starter through some extra method, you're given a Rockruff in addition to your starter, or there will be a third sister game where Rockruff is the only starter. Maybe this third version is where Ash-Greninja and shit come up, so the anime references won't be in Sun or Moon.