As ACMA points out, that figure (which covers the year to June 2014) is up six-fold since 2009, when 495,000 Australians used Wi-Fi hotspots. (The figures don’t cover people using personal hotspots based on mobile networks.)
It’s worth thinking about Wi-Fi hotspots in a corporate context. Inevitably, people will use them for work tasks, so you need to put appropriate security measures in place or require the use of a VPN.
Hit the report for more statistics, including a state-by-state breakdown of available free Wi-Fi services in each state of Australia.