Perhaps iPad based wireless inflight entertainment systems are the way going forward. You can load as much or more content, and there would be significant fuel savings from having an iPad for each seat as opposed to a bulky built-in entertainment system. This leads to lower maintenance costs also which should result in lower fares or the sustainability of a larger network to more destinations.
Conventional seat-back TV or iPad - as long as the content is the same, what difference does it make?