Too hard to tell a complete picture right now, as we don't have any leaks of merit for any final evolutions except for with the starters.
Ninetales and Marowak are pretty much guaranteed. Raichu is a possibility, but I'd like to avoid using it because I've used Raichu so many times. May still happen, though, because Electric/Psychic typing takes two types I usually use two different Pokemon types for, so I could use another new Pokemon with unique typing if I didn't just have a separate Pokemon for both types.
I always use the water type, so that's pretty much guaranteed. Although in OR I dropped Swampert because that's my least favorite water starter line by a wide margin. I don't anticipate that happening with Popplio. However, I also really want Rowlet. It's the most appealing starter here, and also has the most appealing leaked final evolution. So hopefully maybe someone will give one to me? D: (I may end up getting the game late, as I don't really have money to be buying games anyway, so it might work out). Pikipek is cute, too, but I've not always been in love with the final evolutions of the starting bird Pokemon as of late.
Rockruff or Mudsdale are contenders for another spot. I don't know yet.