I think I have definite proof that Yungoos is version exclusive to either Sun or Moon, and that there will be a different rodent in the other version, presumably the one that Yungoos is supposed to hunt.

With today's info, we know that Yungoos evolves once and Grubbin twice. We also know that you can catch Pichu and Caterpie in the first route.

Now, hear me out.
Pikipek is number 10 in the Pokedex and evolves twice, so that has us covered up to number 12 on the dex.
Ledyba is number 20. That means there are 7 spaces in between the two.

How do you cover up these spaces with the pokemon that are on the fist route?
You can't.
Because either combination of Grubbin (3), Yungoos (2), Pichu (3) and Caterpie (3) takes more space than that.

My guess is that these 7 spaces are a 3-stage pokemon (Grubbin, for instance) and two 2-stage pokemon (The only options being Yungoos and another one we don't know about yet).

It could be another oldmon that we haven't seen that it appears. Maybe Spinarak as opposed to Ledyba, or, as I predict, another new two stage rodent Pokemon that is version exclusive with Yungoos (hence why it didn't appear on the trailer or the demo). We all know that Yungoos' dex entry implies the existence of another new pokemon.

What do you ngas think?
There is definitely a gap there for a two staged pokemon, who do you think will fill it?