The media often misreport things like this. This isn't a "federalism" case. It's a sovereign-immunity case. It's already established that states have sovereign immunity, so it's just a question of exactly how far that extends and under what conditions.
Federalism cases are cases where Congress is accused of exceeding its authority altogether, and intruding upon areas of governance reserved to the states. For example, United States vs. Lopez ruled that a federal law prohibiting guns in schools was unconstitutional, since Congress was given no such power by the Constitution in the first place.
I was hoping that when a state goes bankrupt, all legislators who voted for spending must personallly make the debt good.
Talk about instant fiscal responsibility!