The Amazon press release posted above confirms that season 6 will be the last indeed.So this will be 100% the final season? (the next one that is)
Part of me can see the logic behind that, as the books drop massively in quality after the 5th one, and the Laconia plot was the weakest in the series. But at the same time I thought the show could attempt to fix some of the problems, they did so already with previous seasons when the books were at their weakest.
Judging by the clip posted above, aspects of books 7-9 may well be integrated into the final two seasons.
I don't remember that conversation happening in NG or BA