It is strange! For years now, many have been asking for the function to update a Catalog name when Lightroom upgrades. Now we see a request to keep it the same as 'old'. But then we are all individuals with our own 'wants' 🙂
Yes- you CAN change the name of a Catalog at any time, relatively easily (when you know how!).
And follow these instructions from the "Lightroom Queen" to do it correctly-
Since the newly created Upgraded catalog file is stored in the same folder as the catalog file it was made for having LrC automatically use the Same Exact Name would overwrite your original catalog. That is an EXTREMELY BAD IDEA.
With LrC V10 you do get a dialog box to input whatever name you want. I suggest you leave the -V10 suffix to distinguish it from your V9 catalog file (your original catalog) and change the beginning part to something else.
This is what I have done to both of the catalog I use. My main catalog and my Test catalog. Test catalog renaming pictured below.
Then in the File Manager for the OS you are using create a New Folder with a distinctive name and then Copy the newlyu created catalog file and the other folders that have that same name ending in .lrdata to that new folder you created. then just Double click on the catalog file (.lrcat) and LrC will open and load that new catalog from the new folder you placed it in. you can then use the LrC preference to make sure LrC always loads that catalog when it starts.