The U.S. Copyright Royalty Board had been prepared to raise rates on May 15th, but delayed implementation due to pretty much universal opposition. While the board says the new rates will help compensate copyright holders for music streamed online, Variety reports the new fees could be 300% to 1200% higher than those paid by webcasters today.
There's a bill pending in Congress that could reverse the decision, and NPR and other groups have filed an appeal in federal court. But it's unlikely that any decisions would be made before July 15th, which is why NPR and the Digital Media Association are seeking the stay.