Looking at our own sexual revolution, the “having your cake and eating it too” phase would have lasted into the early 2000’s. We are now at a stage where we should begin to observe the verification or falsification of Unwin’s predictions.
Unwin found that when strict prenuptial chastity was abandoned, absolute monogamy, deism, and rational thinking disappeared within three generations of the change in sexual freedom. So how are we doing as we enter the second generation since our own sexual revolution at the end of the 20th century?
As predicted, absolute monogamy has already been replaced with modified monogamy. Common-law relationships are becoming the norm. Although divorce occurred prior to the 1970’s, the mainstream of our culture still maintained the view that marriage should be for life, and common-law relationships were regarded with some distaste. That has clearly changed. Those who actually practice life-long commitments in marriage have become the minority, with couples born prior to the sexual revolution much more likely to maintain a life-long commitment in marriage.
Deism is already rapidly declining, exactly as predicted. Prior to the 1960’s, a combination of rationalism and a belief in God was the norm for mainstream culture. Not only has belief in God greatly decreased since the 1960’s, but there has been a trend to remove the concept of God from government, the educational system, and the public forum. Those who still believe in God sense a strong societal pressure to keep deistic beliefs private. In its place, is a surprising rise in superstition, classified by Unwin as a “monistic” culture, two levels down from the rationalist culture we had prior to the sexual revolution. There has also been a huge increase in the percentage of the population that classifies itself as non-religious, a symptom of the lowest, “zoistic” level of Unwin’s categories.
The swiftness with which rational thinking declined after the 1970’s is astounding. In its place arose post-modernism, characterized by “scepticism, subjectivism, or relativism” and “a general suspicion of reason”. But it gets worse … post-modernism is giving way to “post truth”. In direct contrast to rational thinking, a post-truth culture abandons “shared objective standards for truth” and instead, stands on appeals to feelings and emotions, and what one wants to believe. People can now “identify” themselves as something which flat-out contradicts science and rational thinking and, in many cases, receive the full support and backing of governments and educational systems. Not only do people feel they have a right to believe what they want, but any challenge to that belief, even if supported by truth and logic, is unacceptable and offensive. Here is a quote from Unwin that has become particularly a propos in the last couple decades since our own sexual revolution …
If I were asked to define a sophist, I should describe him as a man whose conclusion does not follow from his premise. Sophistry is appreciated only by those among whom human entropy is disappearing; they mistake it for sound reasoning. It flourishes among those people who have extended their sexual opportunity after a period of intense compulsory continence. 
Summary of where our culture is going, given Unwin’s findings
For the first part of the 1900’s, mainstream Western culture was rationalist and experienced enormous technological advances — from horse-and-buggy to cars; from hot air balloons to supersonic flight and spacecraft landing people on the moon; from slide rules to computers. Unwin’s three main predictions — the abandonment of rationalism, deism, and absolute monogamy — are all well underway, which makes the ultimate prediction appear to be credible … the collapse of Western civilization in the third generation, somewhere in the last third of this century.