So, Mega Salamence is a thing (as many people expected). And it has Aerilate. FUCK. There goes the one crucial weakness this thing had - the inability to use its secondary STAB for anything worth a damn. Suddenly DRAGON is going to be its secondary STAB, and whether or not it'll keep being used is up in the air, considering the sheer destructive power of Aerilate Return. Just think about it. STAB OUTRAGE may suddenly be lacking in power. You don't see X-Scissor on Pinsir anymore, do you? Sure, Outrage is a lot more powerful than X-Scissor, which is why it's not a certainty, but since Dragon is only effective against itself it's easy to be tempted to look elsewhere for coverage.
As with Mega Metagross, it seems like it may not be a matter of IF it gets a suspect test, but WHEN. I mean, Pinsir started from so much further back than Salamence, and look where it is now. The one silver lining that you're going to need to take a good look at if Mega Salamence's stay in OU is going to last more than a few weeks or months is the fact that unlike Pinsir, it does NOT have Quick Attack. It does have Thrash, Body Slam and Double-Edge, but so does Pinsir, and when it's not running Return what it has is Frustration instead (for the sole purpose of frustrating Ditto). After all, while most drawback moves have to compete with moves in the 75-90 range, Return clocks in at an amazing 102. There's also the fact that apparently, its most notable stat boost will be defense (combine that with Intimidate antics for extra fun), so we won't be seeing a Mega Salamence with base 185 attack. I will say this, though: not a fan of the official art, hope it looks a lot better in the game (it has happened before). But hey, it can't be worse than the official Amano artwork for Kefka...
Next up is Mega Lopunny, complete with PANTYHOSE PARTY. Mr. Sugimori knew what he was doing, there's no denying it. Which, of course, makes it all the more embarrassing for the male ones. Anyway, it has a very distinct theme, that being milking Scrappy as much as humanly possible. With a Normal/Fighting typing and the addition of High Jump Kick to go along the likes of Drain Punch, Return and Quick Attack, no ghost is safe! And with the mass exodus of ghosts from the OU tier, this could be a very interesting critter to use in UU. One problem, though, is that regular Lopunny's attack stat is 76. That means they better pump a LOT of points into that attack stat. As in, at least 40. But I think Gamefreak are well aware of what Lopunny really needs, they had to look at its stats when they decided to give it a mega. Either way, another important thing this announcement suggests is the likelihood that the Hoenn Dex expansion doesn't apply only to evolutions of older Pokémon, such as Dusknoir. But I think we could all guess that already. Hopefully we're done with the era of regional Dexes of 200 and under.
Finally, we have Mega Altaria, which packs Pixilate and a brand new Dragon/Fairy typing. Pixilate user, specially defensive, where have I seen that before? It could well be some competition for Sylveon (or at least Florges in UU), though Sylveon's ability to use Wish and Leftovers may be the difference maker. Otherwise, if it gets a decent enough boost in special attack, it may have some potential as a bulky attacker, what with its ability to use Cotton Guard and Roost. Who knows? It all comes down to the stats, and we have virtually no idea what those are going to be.
On the non-mega front, we have some more information on the Pikachu costumes, which appear to behave similarly to the Rotom forms - as in, each costume gets a special signature move. And we're not talking about crap moves like in all those events, either. Well, there's Draining Kiss and Electric Terrain, but there's also Flying Press, Meteor Mash, and the main course, Icicle Crash! Yep, Pikachu now gets Icicle Crash. Pairing it with Volt Tackle would make for a very powerful physical attacker, but with that 90 speed it's unlikely to ever do any damage. That is, unless it DOESN'T keep that 90 speed... there's nothing preventing those costumed Pikachus from having different stats, while not losing the ability to lose the Light Ball. Hey, it's happened before, Eternal Flower Floette has stats that put regular Floette to shame. Fingers crossed!
By the way, if I'm understanding this correctly, there's going to be a shiny Beldum + mega stone event at launch, the same way Blaziken had one at X/Y's launch. So does that mean Metagross' stone will be event-only? If so, then that means Steven is going to taunt you with an event-only thing. And probably slaughter your team, if Diantha's Mega Gardevoir was anything to go by.