Correction: By October 2016, Air New Zealand was no longer a Virgin Australia shareholder. Singapore Airlines hold the stake alongside Virgin Group, Etihad Aviation Group, Nanshan Group (who owned Qingdao Airlines) and HNA (who owned Hainan Airlines).
Virgin Australia has a JV with Delta, codeshares with Alitalia and Virgin Atlantic, which 49% is owned by Delta. Not to mention Richard Branson still has a stake in Virgin Australia so, despite (half-hearted) opposition from SQ, Richard will persuade Virgin Australia to enter SkyTeam as (according to Richard) Delta is Virgin Atlantic's savior.
For someone that suggested Hainan Airlines, as much as I wanted them to join alongside my suggestion Sichuan Airlines, I'm not sure if China Eastern wanted another huge airline in SkyTeam's arsenal. They prefer Sichuan Airlines which is the same size as Xiamen Airlines. But who knows if Hainan can complement China Eastern. If things go well, they can bring HK Airlines, too.
By the time AFKLM Group enters Virgin Atlantic ownership alongside Delta and Virgin Group, maybe 2019 could be the perfect time for SkyTeam to recruit Virgin Atlantic? Royal Air Maroc recently got recruited by Oneworld. I also would love to see Etihad enters SkyTeam despite AA codeshare for Etihad Guest in the future. And Air Serbia, too.