Absolutely agreed, I suppose the point is that fuel is the probably the lowest of the costs involved, in fact there may even be a net benefit fuel wise, as old tech individual screens probably draw more power than Joe Public charging his iPad. The real cost is changing the interior.
In ten years time, the real winners in the maintenance/cost scenario may be those airlines that say "screw the IFE, give them power and internet and let the customers worry about it themselves"
In the interim they can supply iPads or more probably cheapish android tablets to those customers that didn't bring their own.
If I was in charge of a big airlines IFE/cabin department I would be looking to move to that sort of system over the next 2-3 years for any new interiors, perhaps combined with a server shoving a couple of hundered films until in flight internet costs reduce.