I honestly think that we have no choice other than to anticipate older pokes being brought back since there are not enough new pokes to make for diverse possibilities for his team. We have three already, so I will only do the four others, based on previous patterns.
Grass: Clemont has Chespin and Jessie has Pumpkaboo, so those are out. The two left are Skiddo/Gogoat and Phantump/Trevenant. I do not find it to be in Ash's style to have Trevenant, but they could surprise me. I favor Skiddo, though.
Fire: Litleo/Pyroar This could be possible, but Fletchling also attains Fire for it's evos, and none of Ash's birds has ever failed to reach it's full evo. We have had type redundancies in Ash's team before, though.
wild card: This is most variance there can possibly be. We've seen Ash open up to a lot of types lately. His most common wild card, Ground, only has one poke, though: Diggersby. This will have to depend on if Clemont evolves his Bunnelby or not. I don't really favor Ash having Diggersby, though. I see them using this slot for a poke that has a cool evo that everyone likes. There are multiple choices for this.
That's all that would fit the normal pattern of what Ash gets. Sometimes, he gets a late gen capture that doesn't really do much. I'm not too sure what to suggest for that, either, as it is like a second wild card slot. Since these options are so low, though, I think one of these is going to be used for a Mega poke. This could either be an old poke returning to get it's mega evo, or he gets given one like in the game.
