"Within a generation,a majority of Australians will no longer use broadcast platforms at all."
This will mean there will come a day when"linear platforms are switched off for good",Mr Milne said. As the need for broadcast spectrum decreases,it will be auctioned off to telecommunications firms for other purposes - and at least part of the proceeds should be invested in"modern digital media platforms for the public",Mr Milne said.
"As we enter a digital age,Australia must decide whether it wants an ABC fit for the future,and if so,what investments the nation is willing to make to achieve that,"he said.
The bold speech comes as retired economist Robert Kerr finalises a review into whether the public broadcasters,including SBS,comply with the principles of"competitive neutrality"- ensuring they do not enjoy an unfair advantage over commercial rivals on account of being publicly funded.
The ABCtold the inquiry it followed the rules and that its online news operation actually"enhances competition and innovation". However,Fairfax Media contended the ABC undermined commercial news media and produced"clickbait"that was"neither high quality nor distinctive".
Mr Milne used Wednesday's speech to dismiss"the sniping of commercial foes and partisans",which he said had been ongoing throughout the ABC's nearly 90-year history. He acknowledged ABC staff"can and do make mistakes",but the vast majority of the time they were"spectacularly successful".
Communications Minister Mitch Fifield has lodged at least six complaints about ABC content this year,and in June the Liberal Party's federal council voted in favour of privatising the broadcaster.
The heightened tension has prompted the Labor opposition to campaign to"save"the ABC from a further $83.7 million funding cut,in the form of a three-year freeze,announced in the May budget.
The ABC is exempt from a cross-government efficiency dividend but now faces another efficiency review,to be headed by former Foxtel boss Peter Tonagh and former Australian Communications and Media Authority acting chairman Richard Bean.