Of all things that could have happened, we find Arkham being moved to what seems like the middle of Gotham City. Arkham is also apparently overrun by goons and thugs, while the Joker and Harley Quinn are alive and free. The possibilities are endless in terms of what the potential story could be, but what do you speculate will happen?
Yea I think the trailer is just suggesting that the asylum is now the streets of Gotham and that the battle has moved there especially given the fact the Joker has apparently escaped. It would be a tough sell that the inmates of Arkham could take it over once again. I think the Joker will deffinitely play a role in the game, maybe not as prominent though with maybe Two-Face emerging out as the main baddie. It will be interesting to see how they handle Gotham City if it does take place in the city itself. I don't think the game lends itself to be totally open world like a GTA so it will probably just be a portion of the city with some interesting landmarks to explore and the rest being cut off somehow.
Arkham doesn't have to be moved brick by brick, it could just be a temporary set up while Arkham is being fixed from the previous game.
The wall and gate in the trailer are just re-used models from AA, as are the goons running around. Until a new trailer pops up with an Arkham that isn't borrowed from the first game, I'm not going to buy the "hey, let's move it off the island and put it in downtown Gotham" angle.