DL is most likely to be bringing some new loads with it when it arrives, and I would argue that the amount it may take from QF is low (but not insubstantial), however this figure might be surpassed by the business that QF could generate by connecting DL’s passengers domestically. It is also in QF’s interest to isolate DJ from Skyteam connections.
As a former Northwest Plat who moved to Aus, and I can tell you that SkyTeam loyalty in the US is insane. Many friends choose holiday destination based on where NW, DL, KL, CO fly. And business associates who fly SkyTeam would fly QF only because UA's biz product was horrible. Now that DL and UA are moving in with flat beds, I think it's going to put a lot of pressure on QF. However, I doubt much ex-Aus traffic will do DL or UA.
On the flip side, VAus is basically unknown in the US (similar to Air NZ). I always find LA an interesting destination for Aus passengers (no clue why so many people go there - not a fan of the city at all), but 90% of biz traffic will need to connect on. VAus already had a connection alliance w/ NW, but we'll see what happens now w/ the DL/NW merger.
In a nutshell, whether Velocity joins SkyTeam or not, a DJ/VAus and DL/NW partnership is practically a given. VAus is basically only going to sell tickets ex-Aus and will need a partner to ferry it's passengers around the US, and ex-US DL passengers will need an airline in Aus. It's a win-win for both airlines.
Virgin America is a major-urban point to point carrier with very limited (compartively) route structure. While sharing ground facilities with VA at T3 LAX makes sense, extending that agreement to interlining or code sharing would created added costs where they shouldn’t be, and therefore a strategic change for VX. (But if they think they can make a buck...who knows?)
Hmmm... just thinking through this... Is there any other "low cost int'l" carriers that connect two large land masses/countries? None come to mind. I think the different geographies of the US/AUS make interlining almost a requirement, vs a "nice to have" - esp if they plan to move business travellers (which VAus is clearly trying to do with both PE and Biz products).
But no matter what - I agree - it's going to be interesting to watch this one from the sidelines!!!