I don't think its a safe bet to hope anything. iirc, last year, when X&Y released (which released on the 12th - and Coro Coro leaks on the 8th-12th), Coro Coro gave us Mega Tyranitar/Aggron/Kangaskhan/Gengar. I know Kangaskhan was already known since it was revealed a long time ago, but I don't think we'd actually had an *official* reveal, nor did we know stat boosts. Gengar would've been unknown, too, if the games had not leaked early. Not too sure about Tyran/Agg though. I don't think there was an official reveal before Coro Coro, but I could be wrong - so at least those two were officially revealed in Coro Coro.
Basically what I'm trying to say is that last year, Coro Coro basically revealed 4 new megas literally a day before X&Y released, so I'm pretty sure if they've got megas left, then they'll reveal some in this months issue, which is a good thing imo, because at least is shows that there are still megas to be revealed that weren't in the demo.