Given the age of their predecessors, the 747s - which left the fleet aged around 22-23 years old, I find it hard to think of the 330s as old. That said, EI's cost cutting policy, combined with the fact that the 333s can't be updated with personal TVs and other comforts due to weight restrictions, means that they are lagging behind other airlines. Most UK originating carriers, BA, BD, VS and the US carriers, now offer superior inflight entertainment and it does make a difference.
My expectation is that once EI knows the future as far as US access is concerned, which should be later this month, when an Open Skies deal between the EU/US is expected to be signed, it will be in a better position to press ahead with its fleet plan. Don't rule out the possibility of Boeing getting a shot at this. Either way, it's much cheaper to get new aircraft with PTVs fitted - manufacturers will do this as part of the acquisition deal - than refitting existing aircraft.