Will we? 

We have Charizard X and mewtwo X,  and both  have type changes. 

Blastoise X will be water/steel and Venasaur grass/ground. 

Thoughts? :p

They should, but they aren't as popular. And Mega Venusaur kinda sucked, design-wise :S he was just a slightly bigger Venusaur with vines, they didn't even try ;~;

Nah, Charizard and Mewtwo are just more popular, that's all.

They definitely are popular enough,  after pikachu/mewtwo/charizard it's literally Blastoise right afterward! Venasaur comes in the next tier of popularity with greninja/blazeken/lucario ;p

I'm surprised we haven't gotten a Mega Raichu yet, now that you mention Pikachu. Bastoise is a very popular Pokemon, Venusaur has never really seen the same success. But I'd love to see them make a good Mega Blast/Venu variant 

Definitely not arguing that but remember mega blaziken in xy but was in oras too with the other starters getting megas? I can see some thing similar here

We'll probably see Mega Charizard Z.

And then we'll probably end up getting Mega Pikachu lol.

Lol! Ironically I was thinking about triple types, and though it might be too much I can see it happening with an ability via "insert type" power. All the ability would do is add a type where the pokémon gets the resistances and immunities with stabs for that type. 

In other words charizard Z is fire/flying with the ability dragon power. Which now has dragon stab asks as well as added resistances to water/fire/elect/grass!

Not to shabby huh =) 

Poor Raichu