Looks like it. It seems like the game has been fully leaked a good month before Gamefreak even released it. If it is the case, Gamefreak need to be smarter in leaving out content. People will datamine your content. Or the more favorable outcome, they anticipated this, and left out some of the megas as to surprise us when it does happen, but its not looking like that, as we got "mega" Hoopa leaked. I'd be shocked that 2 of the most popular gen 3 pokemon, Milotic and Flygon don't get megas.
Well, as each and every one of their games up until now has been data mined at one point or another, I'd think that it would be a safe bet that they did anticipate this happening. If this was the case, then they either included everything, and don't care that everything is out, or they used an earlier model of the game for the demo. Given the level of protections that they tried to use in XY, I'm kind of disinclined to believe that they don't care if everything is leaked a month early.
A lower level to the theory that they don't care is hinted at by the fact that there was only one 'new' pokemon in the mined information, and they don't consider the move and tutor lists as important enough to hide. In other words, they, for the most part, got out in front of the leaks, and made the reveals in their own terms; I would find this to be much more believable. After all, they had already hinted at things like Leaf Blade Shiftry and HJK Lopunny, so it wasn't that big of a deal. Really, the only thing that they lost here was the information about the stats, and the Hoopa Form.
On the other hand, I can't see it being that difficult for them to, at some point during the production stage, set aside a copy of what they already had, and label that as the demo. In that way, they could include the maps, the relevant Mega releases, trainer classes, the pokemon files, and so on, without having to go back and scrub content that they want to hide. From that point on, they could go ahead and include other features and Megas at their own disclosure. If this is the route that they took, then it could be viewed as them throwing us a bone, and hoping that it will sate us and draw us in, and then blow us out of the water when it turns out that there's another Mega, or the Battle Frontier, or whatever. I'm not sure how likely this, but I'm sure that it's possible, and I don't think it should be assumed that we know absolutely everything now.