I believe the Sinnoh Frontier Brains will be handled a lot differently in the anime than the Hoenn ones were.
Meaning I do not believe they will be spread across a region for Ash to do anymore, and instead he'll battle them back to back. Why? Palmer said he is a Sinnoh Frontier Brain, that means Ash would have to backtrack through the entire Sinnoh region just to find and track down each Brain.
Instead, I can see them being treated the way the Battle Frontier is in the games, where they're all in one place and Ash gets to do them back to back. The problem is Sinnoh has been stretched out to the point of absurdity and there's still possible Elite 4 matches to come, so the Frontier Brains seem to be caught in limbo this time. They have no logical place to fit in, since Cynthia is stronger than Palmer, and should be the final climatic battle of DP.
Meaning I do not believe they will be spread across a region for Ash to do anymore, and instead he'll battle them back to back. Why? Palmer said he is a Sinnoh Frontier Brain, that means Ash would have to backtrack through the entire Sinnoh region just to find and track down each Brain.
Instead, I can see them being treated the way the Battle Frontier is in the games, where they're all in one place and Ash gets to do them back to back. The problem is Sinnoh has been stretched out to the point of absurdity and there's still possible Elite 4 matches to come, so the Frontier Brains seem to be caught in limbo this time. They have no logical place to fit in, since Cynthia is stronger than Palmer, and should be the final climatic battle of DP.