The sixties was a counter-culture. Since then much of SBNR has moved to an “insightful wellbeing” culture.
In that guise, it is looking settled. The proportion of Europeans registering as SBNR seems to be about 15-35%, depending on the question and the context in which it is asked. The US seems broadly comparable, but the religious are more numerous there, so the category “both religious and spiritual” is probably more populous.
In Britain, Sweden, Denmark and Holland, some studies say SBNR now outnumbers Christianity. The UK government is adopting SBNR language in some areas as churchgoing continues its steep decline, indicating some degree of torch-passing.
In other words, there is a danger of getting too comfortable. The challenges ahead are by far greater than those SBNR has faced up until now.