Geographically you are correct but all these suburbs must be in the proposed catchment area for the proposed new team.
My turn to correct your claim that Western Suburbs still exists in the NRL. I've checked this year fixtures and cannot see them. To say Western Suburbs still exist is like saying Fitzroy still exist, I think most people would disagree with you on that.
I would be surprised if the AFL were looking towards Campbelltown, Rosemeadow, Macquarie Fields etc as a proposed catchment area. I'm sure their target would be the geographic western suburbs, rather than the outer south western suburbs.
As for Western Suburbs Rugby League Club, the merged entity may have dropped 'Suburbs' from the name, but are still called Wests Tigers & are predominantly referred to as Wests by many of their supporters. They also still play home games at Campbelltown, whereas we don't see the Brisbane Lions playing home games at Brunswick St or the Junction Oval, or in Melbourne generally.