As other posters have said, I think the focus on China makes sense, given the way that aviation is expanding there.
Personally, I think the other 'gap' (in addition to India - which Goldorak has already mentioned) is Africa. Many African countries have growing economies, surface transport connections are often weak, and there is increasing demand for aviation. ST already has a reasonable presence in Africa (one African carrier in KQ, and good links to Europe with AF/KL, plus a few connections by other carriers). However, *A now has 3 African carriers (SA, ET and MS). My recommendation would be for ST to take up a strong carrier from western Africa (not sure who, though) to complement KQ's presence in the east, and AF/KL's connections to Europe.
However, I've no idea how actual/potential traffic to/within Africa compares to traffic in the other regions that have been mentioned....