I think a new Battle Frontier-type facility would be nice, if only because it'd provide the challenge that more experienced players are looking for, being a place where levels and strict type advantage don't automatically determine the outcome of a battle, but where you need a sound strategy and good tactics.
With Pokemon catering more and more to a more casual audience by streamlining experience with the EXP Share and making EV Training easier through Super Training - both great things, because they're wholly optional and you don't HAVE to use them - I can understand how veterans are feeling more and more left out. A Battle Frontier reminiscent of Emerald's would go a long way towards closing that gap.
Will it happen? I think it's possible. But I don't think it'll be a priority.