Can definitely see both sides of the argument here. LCD's will be a vast improvement but one would think, to remain competitive, UA should invest *now* on this for the future. AC offers non-stop Nth America to Australia later this year also - so while demand continues to be strong for QF & UA on these routes, East Coast *A flyers will have another option when flying/connecting to OZ/NZ.
(My parents flew RTW on *A last October and were extremely disappointed with UA's non-IFE across the pacific, and their charges for alcohol trans-Atlantic. I think they lost a couple of customers there!)
All that said, if the choice really is one or the other (upgrading premium cabins vs including a large overhaul of Economy with IFE per seat), then they are probably making the right choice given the limitations.