According to the anonymous sources, VW's lawyers and federal prosecutors have already held preliminary discussion to reach a settlement before the end of the year. The DOJ hasn't raised any specific criminal charges with VW, but The Wall Street Journal points out that US prosecutors have previously charged automakers with concealing information from government officials and wire fraud.
VW is already expected to pay roughly $15 billion to buy affected vehicles back from customers, end leases early, invest in zero-emission technology, and fix affected vehicles. A settlement on the criminal side of the ongoing case would surely cost more for VW than the $1.2 billion Toyota agreed to pay to close the investigation into its unintended acceleration issue. Since a lot of individuals who worked on VW's emissions-cheating hardware live in Germany, extradition of individuals could also be involved in the settlement.
Recently, the German government gave VW the go-ahead to begin recall work related to the 1.2-liter turbodiesel engine, which isn't available in the US. In spite of receiving German approval, VW is still working with the California Air Resources Board for a fix for affected vehicles in the US.