I think you will find its not becoming a city, rather a regional centre. Big Difference. If you're looking for low risk CG then I'd suggest you stick within the Perth Metro area if its for investment.
Bear in mind Super Towns is a government program at the mercy of politicians. Unless backed by long term private investment and growth it's not really sustainable. Bureaucrats (especially in 'development authorities') are good at writing reports that justify their continued funding but it may be better to discount some of the grander claims.
Northam can be stinking hot in summer and freezing in winter. Not a bad place for an immigration detention centre, and in fact there is one. And it's got great motorsports https://www.facebook.com/NorthamMotorsports
It's on rail and road links between Perth and the east. Still that hasn't stopped wheatbelt towns along there from declining in population. Northam is the main regional centre for pretty much everywhere east from there to beyond Merredin.