The way I see it the bet was about the statement that the drivers for the war were already there in 1995 and that it would actually materialize in the 25 years

The way I see it the bet was about the statement that the drivers for the war were already there in 1995 and that it would actually materialize in the 25 years before 2020 - which it (IMHO obviously) has not. The struggle is still there, but a society-shattering escalation of the conflict has not happened (yet?). The observation that "the rich and powerful have convinced the lower classes to attack each other instead of them" seems like a reasonable tactic for the society (or the rich) to prevent such a war from occurring, and this might plausibly succeed for a prolonged time in the future - as you say, "successfully driven in dividing lines" that are long-lasting. I see Kirkpatrick Sale's position as essentially claiming that the tensions are stronger than the societal bonds that favor status quo and centralization, that these tensions can cause a society to collapse - and the last 25 years have shown the opposite, that an increase in these tensions is still tolerable and does not lead to a collapse.