SQ has always been interested in acquiring a stake in either AI or IC, and even have the infrastructure already in place (through joint venture agreements with an Indian company). Additionally, the existing relationships of AI with VS, NZ and SQ itself seem to point towards that scenario as the most likely one.
CX on the other hand (and by extension the Swire group), have not expressed interest in AI in the past, and will find it a lot harder to capitalize on the "upsides" of the deal (viz. route authorities, etc..) because of existing partnerships and agreements on both sides.
I think SQ will be the front-runner by far, and look for them to be the succesful bidder unless something significantly changes the long-term picture.