The Justice Department has left open the possibility of prosecuting officers or employees of Barclays. But it has agreed not to prosecute the bank itself, in part because Barclays was the first to cooperate in the investigation and has agreed to keep cooperating. Such an agreement makes sense only if that cooperation will allow prosecutors to nail other banks that have been involved in setting the rates, including potential cases against Citigroup, JPMorgan Chase and HSBC, and people who work there.
I don't recommend holding your breath.