It depends on what service level you are at, and where you are. Currently, if you just have basic cable (just your local broadcast channels, and no local channels) then you won't need a cable converter box practically anywhere in the country. If you do get cable channels, then it really depends, and it may even change over time.
Well, maybe. The regulation requires that they continue analog service of some sort through 2012. However, the regulation explicitly allows them to require use of a converter box with analog outputs to satisfy that requirement. So some might not wait until 2012. However, others might continue analog service for the local broadcast channels past that, especially if the FCC allows them to limit how many they carry that way.