Regarding Second Officers for the A340 operation, this is not the way Emirates is going. On the ultra long range flights, the crew compliment will be two Captains and two FOs. (As it stands at the moment).
Because all A330 pilots will eventually be Cross Crew Qualified to fly both types, there is no requirement for Relief Pilots.
There were rumours of a narrow body fleet about two years ago, but that is long dead. As Check 'Six' says - they do not fit in with the route structure. It is more profitable to fly an A330 to Doha with 100 pax but with 20t of freight in the holds.
The Chairman has been heard to say that the A330 is too small for some of our routes already - if you have tried travelling on staff subload tickets, you will realize that he is dead right!