It also depends how much George RR Martin thought it was important.
Remember Tyrion's first wife? they introduced her, reminded her, and then said "nah, screw it all" having him killing Tywin over Shae, while in the book he's pissed because he deceived him for years. So the prophecy may be a case where the authors go "meh, whatever", but they're still reminding it with the deaths of her children so who knows.
For sure it makes sense to Jaimie finally snapping and being in the situation of having once again to stop the sitting king from destroying the town, or maybe she'll pull a Hitler and blow up herself on the eve of certain defeat.
About how the final two seasons will go, "Battle for the Iron Throne first and battle for Westeros later" makes sense, but it all seems so nice and tidy. I'd love for some more messing up of the two impending wars, rather than the Iron Throne being nicely conquered and the winners going "mh, ok, now let's think about the White Walkers".