I know one certain pokemon i'd love to see leave, and another who's looking to get benched for evolving too quickly too.
Two words, Soothe Bell.
Anime=/= metagame, but if you wanna get technical having fire fighing and steel would be more effective when the group gets up to the ice routes intead of two flyers.
Gligar must be pointless too then seeing as how Ash also has Staravia who is going to overshadow it once it evolves because it can still evolve again and therefore will get more attention.
Technically both of them are hard to pull off in the long run because in the end it's two new pokemon to deal with, as we've seen countless times the starter pokemon usually have "issues" with evolution and seeing one evolve not once but twice in one region hasn't been done since Charizard who of course evolved over the span of five episodes and given how chimchar is already mirroring Charizard's past as Charmander i know no one wants to see rapid growth and would rather the evo's be drawn out in which case for Infernape to happen before the sinnoh league(which i know most people want) Chimchar is going to have to be the next pokemon to evolve after Gligar and is going to have to go as early as after the movie, then again we've had two perfect opportunities for it to evolve into Monferno already that the writers went and wasted, and i'm having a hard time even trying to think of another scenario in which it can evolve and the longer they hold it back from going the worse it's chances are long term.
As for riolu, yes no one knows if Ash will get another pokemon or not, the fact they loaded him down so quickly though makes me believe he'll get another(it's not like thier really developing his current guys much anyway, or we would've had at least one more evo by now not counting Vlad coming) and someone could quite possibly get oaked for it, not to mention seeing as how item evo's usually make a pokemon evolve quickly, so if Ash gave it one of his soothe bells it could evolve rather quickly compared to chimchar so who knows as in the end both have problems long term.
All i know is Ash better get one of them, i'm too hyped up for him to get at least one fighting type this region and i don't care who it is, right now i don't care who he gets, but if Chimchar does not evolve at least to monferno before gym 5, then it's too late for Infernape to happen and i will go for Riolu instead as Chimchar will have passed the point of no redemption.