from CAPA (sorry i can't give the link because i use mobile here), CEO of AF said that there's a possibilities that IndiGo will be potential future member of ST.
hmm.. it means that ST will be ended with 6E if failed to get 9W (though i can say that 6E seems more regional than 9W). And of course, it depends from 6E to do codeshare(s) with ST members or not as they're LCC.