That is one hell of a rumour...
Word going around when they signed was that the contract was airtight and bomb-proof from QF's point of view. So I guess it is possible.
Airbus would be pretty miffed but I doubt it would throw the A380 program into any sort of jeopardy.
QF has been pretty upbeat about the A380 though... it is a major feature in any company publications. I doubt it would be cancelled unless there were other plans afoot.... lets roll out the 777 rumour again!