What Pokemon do you think will gain relevancy or lose relevancy in the Gen 3/post-legendary meta?

If they give wonderguard (or that effect) to Shedinja he will be a VERY potion efficient attacker :D

(in the main series games Shedinja can only be damaged by moves that are SE to him, but he only has 1 hp, so when hit he dies)

Other than that: Salamence, Gardevoir and Metagross are gonna be great pokemon.

Metagross is gonna be a new Blissey due to elite stats and defensive typing
Blissey won't be even a problem when Mewtwo comes out
Gardevoir is the new Alakazam, Espeon and also a Dragon slayer. What a unique queen!
Hariyama might be a new Machamp as his evolution should cost less
All the Psychics will lose relevancy as gym defenders.
That's all I guess

Probably metagross, salamance, alataira, slaking, gardevior, flygon maybe. As for legendaries probaly either latias or latios and the legendary trio of that gen. I dont see the 3 regis getting much use but who knows.

I think his question wasn't so much about future Gen 3 mons as it was about what will happen to the already known Gen 1 and 2 mons once Gen 3 is released. Will any Gen 1 or 2 mons lose relevancy or gain relevancy?

If they add abilities, everything will change. If they don't, a ground sloth will beat the shit out of everyone. Unless they give it a custom move