This early on it's almost impossible to tell what older Pokemon are gonna be in the regional dex. They obviously don't want to reveal to many new Pokemon right now so that's why they showed us gameplay with some older Pokemon.2. So far we've seen Pokemon from every Gen other than II in the game. Unless they randomly used old Pokemon to show the battle system (like Butterfree was in a DP screenshot to demonstrate the gender differences).
I don't really care how it is possible as long as it's just possible. They have the habit to put the feature in one game but to take it out in the next one. I was quite disappointed when I found out I couldn't re battle gym leaders in BW. The problem is that we never know if it's possible in the next game or not.3. I've always wanted this. Emerald did almost perfectly with that I reckon, Platinum... Not too bad but I want the freedom to battle any leader I like (although I wouldn't mind a system where you have your own café in an upgraded Join Avenue that friends and leaders visit for you to battle), BW2 I hated for that. Yeah I liked how it was possible, but I wanted EXP from it, and it clearly wasn't canon.
Oh wow. I have never really been such a GTS user myself but that's just ridiculous. I definitely support you with that.Also, I've probably said enough already about the GTS restrictions, but this is exactly why I think they're absolutely necessary.