nope

"My own heroes are the dreamers, those men and women who tried to make the world a better place than when they found it, whether in small ways or great ones. Some succeeded, some failed, most had mixed results… but it is the effort that's heroic, as I see it. Win or lose, I admire those who fight the good fight."

This is GRRM talking about his heroes, clearly talking about Jon and Dany. Does this sound like someone who will go insane and kill everyone and become evil? This is such a trope that GRRM will obviously avoid the "swerve"

The "mixed results" he talks about are also the "bittersweet ending" he has described the ending of the series as. The show ending was not "bittersweet" it was rancid and cynical and nihilistic.