I don't think an emerald remake will arrive so soon. It'll probably be saved for... Generation IX?
After much observation, I doubt GF will reveal mega sharpedo and mega camerupt. GF will tend to hide a few megas in the game without any reveal (it's obvious though, unlike Lysandre, since everyone saw the keystone in Get TV). I have also given up the hope of seeing mega flygon because Lucia has an altaria which got a mega in the same issue, unlike Aarune.
I think it's either the battle frontier or primal rayquaza next month, with the latter being more likely because I have no idea next month is going to be Emerald's 10th anniversary.