Friendly reminder of what's going to happen, like I told you all weeks ago:

>New Mega Mechanic
Double battles will unlock a new type of 'partner' Mega Evolution. These new pokemon will require:
[a] Their Mega Stone to be attached
To be in a battle with their counterpart (either as a partner in a double/triple battle, or as your opponent)

>New Megas
The new Megas will be unique because both pokemon will share the same Mega Evolution. We've already seen this from the source code of X/Y with Mega Latios and Latias. So what's the reveal list?

[a] Mega Latios and Latias
Mega Plusle and Minun
[c] Mega Lunatone and Solrock