If Qantas have been making "hundreds of millions" even during tough times, and doing that on very expensive equipment, service levels that are perhaps a little jaded and with constrained capacity....then if VA get the service and price levels right they will do well and the market will grow. There costs will be very very competitive.
No doubt at all QFs market share % will fall but it will be off a much bigger base which will grow even more once the 787s hit the various slightly more boutique routes (i.e. those other than MEL/SYD to LAX).
That will be a whole new paradigm because eventually......one day....SIA wil join the route. Best for all 3 Australian carriers (QF, JQ and VA) to have their acts together when that day comes.