No the regions should not be reduced on pgc because of that.
The reason is that the regions in pgc are in countries that have regions the same as they are on geocaching.com . So pgc will convert if gc.com converts. My guess is that is unlikely that gc.com will change anything.
The cases they are not the same as on gc.com is when gc.com has not regions for caches and pgc does. For example Finland has no regions on gc.com but pgc have regions