Touhou is a big deal in Japan, yes. I am not denying that, but to say that even there, it's bigger than Minecraft, is pretty ridiculous. It doesn't matter the longevity. No, Steve and Reimu aren't locks, and one happening before the other isn't guaranteed. That would be a presumptuous thing to assume. That said, Minecraft is massive. I think you're seriously underselling Minecraft here. It's ridiculously big in Japan, as well, and I'd dare say it is moreso than Touhou by a landslide. Just because something has existed for a longer time doesn't mean that it's more popular and more of an icon.