On the surface it seems that the phone companies will be most affected. However, keep in mind, due to FCC regulations phone companies cannot do anything to retain a customer when cable companies submit a voice number-portability request. So whether it takes 1 day or 4 day, they lose the customer anyway.

The real twist is this: when a phone company sells triple-play service to a cable triple-play customer it submits to the Cable company a request to port the number. But the customer has to call the Cable company asking for the Data and Video service to be disconnected. The Cable companies go all out in these 4 days to offer very aggressive retention offer to the customer. As a result, the customer has a higher likelihood of canceling the telco triple-play order.

Due to this new rule, Cable companies will have only one day to target the customers, so the customer is less likely to cancel the telco triple-play order. So I would expect the Cable company triple-play churn to go up.