Others will certainly step in to fill the service gap for VOiP, cable companies have provided some of the pressure on Vonage along with traditional phone companies with their "me-too" services.
Following are two articles that reference other options, while we wait to see what happens when the smoke clears with the courts.
These are reviews of free, low-cost, or Skype-like services: Ten Alernatives to Skype, and 10-Skype-Alternatives. Gizmo is not great, and I have yet to test Jah Jah and GoogleTalk for lack of a peer-to-peer connection.
Resources for Portable Professionals and Extreme Telecommuting™