The "Pending" status is a suppressed No Result. It indicates that a result has not been received for the backup but it is within its user-defined "No Result Threshold".
 
A backup will transition from "Pending" to "No Result" once it has exceeded the number of days defined in the "No Result Threshold".

Is this something that may/is going to replace No Results?
No, it will not be replacing the No Result status.
 
What is its specific purpose?
It provides better visibility into backups which have not received a result but are within their user-defined "No Result Threshold".

This new status provides a better gauge for actionable statuses and delays non-critical issues while still being aware that expected results are missing.