If they hold with their current precedent they will uphold the law as written, meaning that nothing will change. Prior precedent from ALL the justices on the court specify that you need to read every line in a statute in the context of the rest of the statute, and in a case where the meaning is unclear you defer to the government's interpretation if it's reasonable.
I imagine it will be either 5-4 upholding or 6-3 upholding, although again it should be 9-0 in favor. There will be no reasoning with Scalia, Thomas, or Alito.
Scalia is a piece of work, huh? The circular reasoning is astounding. He acknowledges that it should be fixed, asserts that congress will fix it if the court breaks it completely, ignoring the reasons it's come to him at all- Congress has already refused to fix it.
The whole thing is just pandering to a well propagandized base, him being part of that. The court has already provided their imprimatur. They'd damage the institution itself going back on it now.