Clearly AC is moving to smaller J cabins in their wide-body fleet, only 20 seats in the 787. If the 777 HD is an example, I predict that when the current 777's are refurbished the number of J seats will be reduced and a PE cabin added. Also expect, once a majority of the 787's are in operation, a one cabin upgrade policy. This will will be severe for companies where only Y class travel is allowed.

The current narrow body mainline fleet will probably not change but look for fewer J class seats on the new 737's.