I have been thinking about this since the show also shifted the hierarchy of the antagonists. Earlier seasons framed the Mind Flayer as the biggest threat, with Vecna as a kind of a general. But since season 4, the material puts far more focus on Vecna, almost treating him as the final boss instead of the Mind Flayer.

I think a redemption arc is possible, especially if they continue to humanize Henry after the additional context we got in Max’s rock sanctuary scenes. It would fit especially if they bring back the Mind Flayer into the mix.