Streaming Compression Math
I believe the definition of “predicted” you are using does not match how the term is used in video compression. A “predicted” frame is just a frame that can be reconstructed using information from previous frames, along with some additional data. The frames are not zero sized, but that are smaller than key frames. You can have as many predicted frames in a row as you want. A key frame is usually periodically sent because of error propagation. If there is a transmission error and the video becomes corrupt, a key frame can fix it. 

Also keyframe interval and bitrate have a slight correlation, but they are independent variables and not much information can be assumed about one given the other.