Kinda sorta. I remember for Black/White's demo, someone posted a screenshot of a double wild battle(which was rare in the demo, considering you needed it to be Winter to access the dark grass, and seasons were random in the demo), and within the battle was a Munna and Audino. Everyone thought Audino's design was fake, since they were rumored something differently, but Audino is still the same ol' Audino.
There is a good chance that someone will take this advantage of proclaiming things they've seen in the upcoming demo which they really didn't. I say just stick with PokeJungle when the weekend passes by, since they'll have people trying to cover as much as they can whenever they can.
Edit: To add on, I believe the demo will probably be around 10 minutes per run, to allow the player to be able to use a few mega evolutions and to explore their surroundings as they play through. Pokemon demos have never been long at all, and usually contained only one town/city and a route, so this will be relatively small I'd imagine.