Its really going to be a budget/money issue. Would you as a developer want to update a game for new hardware or build a new game. It will depend if updating will net sales because development isn't free. The time and resources needed to update a game to a new device many not be worth the amount of time, resources and money it takes to port at least not in the short time frame. Probably the best well received bigger games will see a port as they can pretty much sell it twice but for smaller games not so sure.