Anabelle was before snorlax but it could be a hint. I don't think it was though. I still bank on the BF being back.
And the Corless probably means nothing related to the dex as it came after.
Now for that new, it's certainly unique. It's slip up to me is the underwater city thing. Another fak leak have and I don't see it happening because of that. We will see though.
Anabelle would be better hinted for something related to Alakazam, or even Latios to be honest. I usually forget she has a Snorlax.
Now, there's a couple of arguements to why the Battle Frontier wouldn't be coming back. First of all, it skipped two generations, however you could say that PWT filled it's role in Gen 5, while Gen 6 was just rushed so they couldn't fit it into ORAS or make a Z version. And second because of what Masuda said about not seeing a point in putting it in, as only a small percentage of players would appreciate it.
Now on the other side, there's a chance of it returning for many reasons too. First of all, since it's possible that they
wanted to put it in ORAS, but simply didn't have enough time, they might want to put one in SM to make up for it. Second, they spent a LOT more time working on these games than they did on XY and ORAS, working since XY's release I believe, including all of 2015, they skipped a year just to work on these games which fills me with hope that they'll be filled with content. Third, since it's the 20th anniversary titles they may want to appeal to all types of fans who stuck with them through the years which means the 3rd-5th gen crowd who spent many hours on the battle facilities and even competitive players. And finally, maybe they heard all the outcry from fans about the lack of battle facilities in 6th Gen, I mean, it worked for Trainer Customizations, so why not the battle frontier? It really does seem like they are listening to fans this time around, bringing back old features, throwing a treat to Snap fans, giving a lot more depth and lore to Pokemon in general, changing up the formula, and again bringing back a more serious and interesting story like Gen 5 (hopefully).
That all said, I still really really want to keep my hopes down and just take the games for what they are when I get them, if they have a Battle Frontier or PWT, hooray!!! If not, I'll try not to let it ruin my experience because these games still look super solid.
P.S sorry I had this kind of rant thing in my head for a few days so sorry i unleashed it on you lol