As has been mentioned, the airline will be run with hand me down 772s from SIA. If the economics are so great as you say they are, then why did SQ replace them with A333 (as the interim for the delayed A350) into secondary Australian cities when they're effectively the same sized aircraft?! (SYD/ MEL don't count as they actually need the larger 77W or A380)
The thing is, they can afford to target the market with the aircraft because they can cram in 10 abreast and thus so many seats. Good luck getting that many bums in seats with the size and payload restrictions of the A333!
I would love to see VA 77W flying all around Asia, but the truth of the matter is that for the relatively new carrier they are (albeit the fact they harness the Virgin brand power) they are relatively unknown. Who cares what SQ/ CX are up to, they're flying in mature markets (of which the capacity is needed because SIN/ HKG are mainly hub ports) with a very well established brand which Virgin will not have for many, many years. Further to that point, when Virgin do start flying into Asia, my guess is it will be primarily to/ from secondary ports- so for the short term at least I think it's A333/A332 all the way.
Disclaimer: I'm in no way disputing the utter awesome of the 777 series, It's just the efficiency isn't there over medium haul routes (ie: AUS- Asia). It was built as a long haul aircraft, which is why long haul, there's nothing in the same size category which can beat it *waits for A350*