Personally, I think adoption will be pushed strongly by the usability of the fiat system itself. Countries struggling more with inflation today also tend to have higher bitcoin adoption. With that being said, you can wonder whether it is adoption on the individual level or on state level that will be best at predicting timelines. From the nation state perspective I can imagine adoption could be realized extremely fast - within ‘one generation’. However it requires fiat to die due to inflation with no way of doing a 2008. That phenomenon sets the timeline dominantly.