From what we understand, the performers in both attractions were notified of the change already by Disney's Hollywood Studios' Entertainment department.
The other rumor we are hearing is that the cancellation of both events is because they're going to work on backstage roads so the floats cannot move around.
If the reports are true, this would mean there will be no afternoon parade in Disney's Hollywood Studios for the foreseeable future. Pixar Pals Countdown to Fun has been running in the Studios since January 16, 2011. Disney Channel Rocks first debuted on October 22, 2010.