Won't all previews need to be recreated using this technique (simply rename the file)? In windows (maybe mac as well) a subfolder below the folder with the subject catalog, will be named "[catalogname] Previews.lrdata" Renaming this folder in conjunction with the catalog name may avoid the need to recreate all of the previews.
untested.
Followup: Tested and confirmed. Renaming the Previews folder in conjunction with the catalog file rename avoids the need to recreate previews. (Windows Vista 64, LR 2.3RC)