Renjith,
More or less any object can be cloned (copy and pasted) and given a new name, but that isn't the same as renaming, since the original will still exist (until deleted.)
Unfortunately, the name is the Primary Key used to reference the object both inside the configuration and also in the databases. I guess you could hack the database and perform some kind of update to replace the old name with the new one (it is, after all, SQL) but you run the risk of breaking dependencies and such an action would probably not be considered to be supportable, I'm afraid.
Another option might be to create a customized version of the report, which combines the two sets of statistics and displays them using only the new name. For details on how to customize reports in this way, please consider attending the 1-day PureConnect Custom Reporting class from Beyond. Unfortunately, this won't, however, allow you to use the old Workgroup statistics to generate schedules for the new one in WFM.