disagree with you....the supreme court all ready has a good idea how each individual member will vote. hearing arguments is just allows the justices to look for mistakes in logic rarely does an argument actually change the opinion of a justice that is why they have to stay mum to direct questioning about how they will vote to an issue coming before them.
The legal issue is whether the validity of executive action on immigration should be based on the grounds stated in the order or whether extraneous evidence of intent should be allowed. I believe five votes were lined up to follow the first rule, which is what the case law says. But Trump just tweeted that the grounds offered in the order are not accurate but just put in for "political correctness" and that the order really is a travel ban contrary to DOJ's position. That might be enough to flip at least Kennedy. Dumb move.