tgdxb!
I think I am right in saying that the cockpits and controls of modern day Airbuses are virtually the same therefore it is relatively easy for a pilot to transfer between types. Obviously the handling characteristics of a 319 will be different to a 340 but the controls will be almost identical.
In the case of the 380, I imagine most airlines will select from their existing 330 and 340 drivers to make the quick transistion!!!
FBB