i would presume someone would go and tow it in. you couldnt just leave it to float around as it would become a hazzard

I would think it unlikely that the rescue vessel made any attempt to either tow it or sink it therefore until it sinks or someone claims salvage rights it becomes a hazard.

Would depend on the weather and the boat conditions at the time. If the boat was still worth recovering versus the costs involved and if it was possible to get someone on board to open the valves to scuttle it.
My guess its still bobbing around in the middle of nowhere.

i think i remember reading that it would simply be left but could be mistaken

Many years ago I had the utmost joy and pleasure (tongue in cheek) of going for a jaunt down south to welcome to Australia Isabelle Autisier and Tony Bullimore. Both vessels were left as they were. Talk was made to sink them, but we were not allowed.

todays paper says the family have given up efforts to raise the money for recovery of the yacht

Didn't they also say that Aust has to bare the costs of the rescue as we answered the call. Something like 80g odd, maybe more and she wants to do it again. I saw something on tv the other day about how they explained how Aust had to pay for it, really got my back up.

Let the navy use it for target practice. Once they get there eye in, head north and blow some of those boats away, that are full of shark fin.

Aust Sea Search and Rescue area is the biggest of all the countries of the world, just our luck for being so isolated. Think it goes down to Antarctica across to Heard island or another Oz protectorate nearby then northward to about half way to Africa.