I'd say the people buying a coffee from Coles/Woolies would be a different clientelle to coffee shop/cafe patrons.
They'd be more your 'on the run' customers I'd say, like those who buy coffee from the BP, Maccas, Muzz Buzz, etc. who btw appear to be doing equally as well as sit down cafes.
I know my local BP is constantly making coffee for those passing through.
Aus is becoming like the USA was, and is - when we lived there; everyone running around with a "to go" coffee cup stapled to their hand 24/7.
What I did notice was they were particular about the coffee standard....it has to be really good.
If Coles/Woolies can get their act together and deliver a really good product, and keep the price fair, there is no reason why the patrons won't grab a take away, or even make a trip there to get it.
This is assuming there are not many or any specialty coffee places nearby where people already go for a good brew....folk will still go to those places if they are truly coffee snobs like we all seem to becoming.
When we went up to the Gold coast for a holiday a couple of years ago, we stayed at a Big 4 caravan park which had 24/7 help yourself coffee. It was average, but if you were desperate.... (we are coffee snobs, of course
).
We are always up pretty early, and their restaurant wasn't open at that time for the "must have" first thing coffee,
So, we/I got in the car at 6.00am and drove about 5 km's to the nearest specialty coffee place which was always open at that time for the locals going to work.
Personally; I can't see them putting other better coffee houses out of business.