I'd love to see EY join the Star Alliance but I feel caution.
Remember that Qatar were almost at the point of announcement after quite a deep partnership with LH but then at the crucial point LH pulled the plug and refused to allow QR to join. Now LH has a partnership of similar vein with EY, possibly based on some common work after the demise of Air Berlin and while LH has done joint work they have always resisted including in the courts the influence of the Gulf carriers. If EY joined *A it may be that EK would be able to overturn the protection LH enjoys in Germany and gain wider access than their current four points which I think are FRA, MUC, DUS & HAM.
Equally, as the Gulf is not a destination in its own right for many SQ who have no doubt lost out to the Gulf carriers too are noted not to be keen on having EY on board. They and LH are big players with a lot of influence. Maybe they will think it better to have an ally now rather than not but I wouldn't hold my breath. Air India might also have reservations about a Gulf carrier.
Let's hope EY do join though, from a passenger's point of view, they would be a great addition.