Sure, but it doesn’t matter how much probability mass atheism gets, because the religions are the only ones offering infinities*, and we’re probably interested in best expected payoff, not highest probability. If religions have 1/10^50 residual probability mass and atheism has all the rest, you’d still probably have to choose one of them if at least one is offering immense payoffs and you haven’t solved Pascal’s Mugging.
*I guess one could argue that a Solomonoff prior assigns a zero probability to truly infinite things, but I’m not sure that’s an argument I’d want to rely on (also I know Buddhism offers some merely vast numbers, although I’m not sure they’re vast enough, and some other religions do too, I’d imagine).
That’s fair. I guess adopting exponential discounting is also good enough to rule out Christianity. Not about trying to live infinitely long, though—it would depend on how much believing in Christianity would hinder you in achieving that. (Same for other religions that don’t promise sufficiently amazing bliss.)