Its a remake of gen 3 they never remake all 3 games from the respective gen but incorporate the 3rd games features into the remakes (atleast they have in the past) and despite starting on yellow, battle frontier has been my single favorite thing in the entire series of games so i rate it far higher than the pikachu in yellow 13 years of pokemon and all i want is to battle in battle dome and pike again with the new features is that too much to ask for 
Edit: Basically what i'm saying is it will not feel like gen 3 to me if it lacks frontier and i guess that's true for others as well given some of the reactions on reddit to the mere potential that its not in the game. I don't want to sound ungratefully but delta saga and a hd hoenn wasn't what i wanted in the remakes, frontier was. I have been dreaming of returning to hoenn frontier with garchomp and lucario etc since gen 4 and was so sad in gen 4 when its frontier lacked dome if the remakes lack frontier altogether it really will crush the dream I've had for so long into dust and i'll prob end up sobbing in bed for the whole weekend.
Edit: Basically what i'm saying is it will not feel like gen 3 to me if it lacks frontier and i guess that's true for others as well given some of the reactions on reddit to the mere potential that its not in the game. I don't want to sound ungratefully but delta saga and a hd hoenn wasn't what i wanted in the remakes, frontier was. I have been dreaming of returning to hoenn frontier with garchomp and lucario etc since gen 4 and was so sad in gen 4 when its frontier lacked dome if the remakes lack frontier altogether it really will crush the dream I've had for so long into dust and i'll prob end up sobbing in bed for the whole weekend.
