Ok. Don't ...(wait for it)... flame me but I think Ash will get Magmortar.
I won't flame you but allow me to explain why it ain't plausible.
First off all, it will make the DP team fail plain and simple, heck any two time evolver will do it regardless, and before anyone tries to say anything let me just say again i find it rather ironic that the Ag team came out looking so good when only one pokemon had to evolve twice and the rest only had to evolve once sans Torkoal, so it would seem the less evo's the better the teams gonna get in the end.
Second of course is capture and development, If Ash does catch it, it will be Magby, Magmar is capable of pwning Pikachu in combat, and given Pikachu's "weakening" upon coming to sinnoh i doubt he could take one on, sides the writers love developing most pokemon in thier base forms as well, now let's look at development, i see at most 3-4 more evo's total for Ash while he's in sinnoh, but the problem is Aipom and Staravia are gauranteed two of those since Aipom has to evolve, and Staravia wouldn't had gone so early if the writers weren't planning on having it go again so that leaves as the most two more, yes magby could take those two, but that would mean Turtwig would be screwed over, and also the remaining capture that is made as well.
Given that this is a new region it's time to see the new guys be developed, not old schoolers who have no business being on the team like Aipom whos bad enough already, sure the new guys that Ash has aren't really doing well right now but even so that doesn't mean they should take a back seat to an old schooler cause then we weill be looking at a jouto repeat as several people seem to also blame the lack of development the jouto pokemon got on the kanto starters (Especially Bulbasaur) stood around longer than they need too, we don't need to go through that again.
Also why in gods name would Ash catch a pokemon that he's never shown intrest in getting before after he's interacted and battled with on several occasions in the past, now i know what some of you are going to say..."OMG what about Aipom" well two things. 1. Ash never interacted with it or battled with it as much as he has Magby/Magmar(he saw it one time in jouto outside the movie and all he did was get a tear from it, that's it), and 2. It got caught during a filler saga when it didn't matter what Ash caught, now that Ash is in a brand new region which premotes new gen games what he catches does matter and he has always caught new pokemon that evolved into new pokemon for his team since it's thier time to show us what they can do, if they want to have old schoolers being used then let Dawn or Paul who probably haven't been outside sinnoh get them since like May and the kanto pokemon they would be new to them but not to Ash.
Then of course theres the fact it evolves through an item and trade evolution as well, and while i know the writers love to "Bend" the rules on trade evo's alot, Ash has still never captured a pokemon that evolved through unnatural means, and why should that be broken in favor of a type the writers apparently don't seem like outside the starter quad(and heck even they tend to suffer on occasion too), not to mention it ruins the suprise factor, Ash still had a choice in hoenn of what fire pokemon he got cause they could've given him Numel, and heck they could've given him another water pokemon instead of corphish too, they still had choices to keep people guessing.
Whatever Ash's last too pokemon are i want them to be ones that suprise and make people excited, not something that's just gonna eliminate the suspense and cause people to get angry.
Cause it's the only new Fire Type other than the Chimchar line, and because Gary has an Electvire.
And Ash should get shellos since it's the only other water pokemon am i right?
Not to mention Gary has a magmar as well that could be evolved. That's another thing, Ash doesn't catch the same pokemon that HE KNOWS his rivals have, and he(and us all) didn't know about Blastoise until AFTER Ash caught his(Same with Krabby too), not to mention most assumed his starter was Umbreon and that they had taken the yellow route of the games until the jouto league.
The Magmar and Electabuzz lines are counterparts to each other so it sort-of makes sense that he would get the Yang to Gary's Yin.
Why is it that just because the two lines were given new evo's that people now regard them as rival pokemon when the lines haven't clashed in the past? the only two rival pokemon in creation ar zangoose and seviper and i don't recall Ash getting zangoose solely to fight Seviper either.