Serebii just posted the corocoro magazine scans for Pokemon Omega Ruby and Alpha Saphire.
I absolutely don't know how I feel about mega Swampert and how about them trainers? This'll take some getting used to. Check out that mega sceptile though.
Click the link to read Serebii's write up. I could copy the whole article here, but I'm lazy and mr. Merick deserves his cred.
Edit aditional info from bulbapedia
Mega Sceptile: Grass/Dragon - (Lightning Rod)
Mega Blaziken: Fire/Fighting - (Speed Boost)
Mega Swampert: Water/Ground -(Swift Swim)