Is there Legislation in the Congress to permit Illinois or any other State to declare bankruptcy?  Until Congress passes such a law and Trump signs it, it can't happen.

They refused to do it for Puerto Rico last year, another Democratic stronghold that overspent on government programs and employees.  

Has a legal opinion regarding both the 10th and 11th Amendments to the US Constitution and State "Sovereign Immunity" made it through the US Supreme Court?

Numerous legal scholars have raised significant questions about any State's ability to submit to the authority of a Federal Judge in Bankruptcy because of  those two amendments even if Congress passed a law permitting it.