SM may win if and only if the they have erradicated the terms in the contract deemed unfit and unfair to artists back when they've lost against Han Geng. There is a big possibility they haven't especially after it has happened again. SM might have removed the terms that were specified back in 2009 but if it happened again there is a bigger possibility that they still haven't. Just sayin'

BUT in the event that they do win against him, he will still be bound by the contract and unless SM says otherwise, legalities say he should return. considering the damage that has already been done, if SM calls the shots and be its evil self then Lulu's gonna pay for it and it's not gonna be a small fee. Poor baby. He's just another one of those victims lured by that blasted company

Well, my sister said if SM wins, he will probably rejoin SM or leave but he has to pay. SM might also start to be more fair.

If that happens, Luhan can still break the contract with SM, but will have to pay the fees for the nullification which is probably more than he's earned as an EXO member, meaning that the best thing he can do (without going into debt) is to either rejoin EXO (which is highly possible, unlike Kris' case since he left for health reasons) or to continue working as a soloist beneath them. However, since he started the lawsuit, SM can still ask him to compensate the damages to the company name (which is a LOT considering the stock drop).
Basically, it'll all depend on whether SM will be willing to take on the damage alone (I don't think they'll charge Luhan though. It'll be like binding him to a lifetime of servitude).

he will not earn any money i guess bt he sure is leaving. sm wont n cant have him back!!! that will b soo unhuman!!!