The issue before the Court is a Federal question, as it involves a federal statute. It is not a Constitutional Question. The Court already wrongly found Obamacare, as constructed, to be Constitutional.(a tax)
I predict it will find in a 6-3 vote that the statute is ambiguous, but under agency principles and the Cheveron doctrine, the IRS “interpretation” of the applicable provisions is consistent with the “intent” of Congress, and thus deserving of deference. (it could be 5-4, but I will go with 6-3 — Kennedy and Roberts joining)
I disagree with that outcome, but that is my guess.