Certiorari was improvidently granted. Eight days after hearing oral arguments in Madigan v. Levin [Briefs at SCOTUSblog], the US Supreme Court issued a one-line order: "The writ of certiorari is dismissed as improvidently granted."
The Court had granted certiorari to decide whether state and local government employees may avoid the federal Age Discrimination in Employment Act’s comprehensive remedial regime by bringing age discrimination claims directly under the Equal Protection Clause.
Dismissing the writ of certiorari has the result of simply leaving the 7th Circuit's judgment alone, without deciding whether it was right or wrong.
I explained earlier why the Court probably would not decide this case on the merits: SCOTUS unlikely to decide ADEA-vs-constitution question.