Downlights themselves aren't inherently dangerous, but older halogen downlights installed without the right clearance or fittings are a recognised fire risk in Australian homes.
Halogen downlights run hot, and if insulation is packed too close, or the fitting isn't rated for direct insulation contact, that heat can build up in the ceiling cavity over time.
LED downlights run significantly cooler than halogen, which is one of the reasons the switch to LED is recommended as both an energy-saving and safety upgrade, not just a cosmetic one.
A licensed electrician can check your existing downlights and ceiling insulation clearance, and quote an LED downlight upgrade if needed.