CCQ should allow an A330 or A340 pilot to fly the A380 with only minimal training.
"CCQ actually allows an A318 pilot to fly an A346 with only a very short conversion course as all modern Airbuses use the same cockpit architecture."
That quote was from Scroggs, a Virgin A340 Captain who I was talking to about whether he flies the A343, the A346, or both. He flies both due to Airbus philosophy/comonality.
As for when the A380 arrives, I'm not sure about EK, but I think Airbus pilots at VS will benefit from mixed-fleet-flying. I.e. they'll be able to fly the A343, A346 and the A38X.
For a 777 pilot, I presume he would have to go through a full type-rating course.