Current Team
Pikachu - Obviously he is staying, first pokemon Ash got and will always occupy a slot in his team.
Samurott - Rather Oshawott evolves or not I see it not leaving Ash team during the duration of the Unova saga, be it Oshawott personality or that it being a future power house to Ash team. I am hoping that this is the first fully evolved Water starter, but who knows.
Chaoboo - I don't know if Tepig will evolve all the way but I see it evolve at least once, so then at one point Ash may face its trainer and Tepig will prove the trainer wrong that he was weak.
Janovy - In my eyes she has already proved to be a strong pokemon to Ash team as she held her own against Trip team compared to the others on the team at that time. For some reason I get the feeling she may evolve all the way to Serperior. I am curious too see how she will do against a third stage pokemon in Gothitelle.
Zuruzukin - I intially thought it would go to Iris, but it seems like it will be staying on Ash team. So at this point if it stays and goes through the battles I don't see why it won't evolve eventually. Yes it is a baby, but Ash got this baby at the beginning of the series.
Hahakomori - It usually doesn't take too long to raise Bug pokemon, so I don't really see Ash taking too long to get Seawaddle to its final stage.
Current Subs
Hatooboo - Depending how often Ash rotates I could actually see Pidove reaching Kenhorou. Also considering Trip got his Hatooboo by Nacrene City.
Hopefuls/Pokemon Yet to be caught
Waruvial - As a Sandile I was hoping he would catch it. But it seems like that was not the case. But it has shown interest in Ash and Pikachu so I could see him wanting to be with them at some point in the Saga. So if Waruvile is on his team I see it evolving to Waruvial and being a power house down the road.
Goruugu - I am really hoping at some point Ash runs along a Gobitto and it evolves to Goruugu. But at this point it is a long shot. Just a hope since it is one of my favorites.
Kirikizan - First Steel type for Ash please! I <3 Kirikizan yes obvious bias. He is one of my favorites so if he got one or Komatana I would still be happy.