Because the generated target files for an IP core will have names based on the IP core name, changing the IP core name could cause linking issues.
However, if the IP core name is the only thing that needs to be modified, you can effectively change the name by making a copy and then deleting the original.
To do this, right click on the .xci file and select "copy ".
Type a new name.
Once the copy has been made and added to the project, removed the old IP core.