how does it work to get the upgrade discount? I don't want to risk buying if for the full price by accident. And is there a time limit for it
Clicking on the link in the email brings up a page showing the price before and after discount. Andy did say in the email that the special deal was until Aug.31 so I don't know why "47 days left" is shown. The discount is %50 whether US, Aus, etc.

"Original price was AU$119.95, the current price is AU$59.97. 50% off • 47 days left".

And I don't think that there will be any updates to AR 6 in the future.
As I understand it AR6 will be supported but no upgrades as ARV is the new AR7.