Personally as much as I’d love to have it, I am extremely doubtful that it will happen, at least this century. Maybe far far in the future, at least after 2150 (that is if there isn’t some new mode of transport by then), but I don’t think that anything beyond SRL East will actually be constructed in my lifetime.
Have a look at the Metronet project in Perth. Massive investment in rail infrastructure is possible if you keep at it. Metronet has already built/rebuilt 6-8 stations, a rail line to the airport, and most of another major line.
A fleet of new locally built trains are in final tests.
It takes time and money. It can’t all be done in a single term.