@GraemeStuart given Musk's prior statements about living in a simulation, I don't think he's specifically talking about Christianity's god. Just, whoever/whatever created this playground we're living in. Most people call such a creator "god"; it's a label that fits. But buying into the rest of the religious stuff? Heaven, hell, specific creation myths, Jesus, etc? Eh, would need to see some direct statements from him on those.
But this market isn't constrained to Christianity's god. Looks like it should resolve YES, regardless of how much I was expecting a NO.
Almost there is a huge stretch, although I guess he can always pretend to believe in God (in one of) the way(s) normal people mean it, and then pivot to Spinoza's "God" or whatever later.
At any rate, 2025 is too soon if I were to guess, although he's certainly unpredictable.