This is a vast yet exciting query.
Firstly, we need to get rid of the notion that 'belief systems' are restricted to religions and religious behaviours. Whereas religions comprise believing in some supernatural phenomenon that the believers ascribe to dictate the real-world incidents without any direct evidence of it, there can be secular belief systems that demand evidence before being faithful to the theory or the process. In this regard, we have to concede that even non-religious people have robust belief systems, albeit standing on the logical and evidence-based grounds. Hence in the truest of sense, there will never be a non-believer human being in the world.
Secondly, when we take religiosity as one of the many forms of a probable belief system (and eventual behavioural manifestations), we need to understand the evolutionary utility of something as culturally and sociologically consistent as religion. As Dr Robert Sapolsky, the celebrated Stanford neuroendocrinologist and acclaimed author explains in his 2017 book 'Behave: The Biology of Humans at Our Best and Worst', the religious beliefs that have independently evolved across all human societies dispersed all around the globe serve as a kind stress-busting aid to the individuals in the society. When we believe that there is something, someone, responsible for all that goes around us, it vastly reduces the stress that we have in our lives that exists because of our cognitive limitations to understanding the causalities of the natural world. The notion of the existence of a benevolent deity offers a feeling of 'control and predictability', Sapolsky posits in his book, and this benevolence is partial to specific in-groups. For its ability to form social groups and explain reality in tidy (however inconsistent that explanation may be) ways, religions have "undeniable health benefits", and hence they are evolutionarily useful.
But with the advent of modern knowledge and the development of science and other rational forms of understanding the natural world, why are religions still lingering around? Will they continue to exist far into the future as well? To answer these questions, let's look at the data and trends available:
1. As of 2018 -2019, 4% of American adults say they are atheists when asked about their religious identity, up from 2% in 2009.
2. In Western Europe, where Pew Research Center surveyed 15 countries in 2017, nearly one-in-five Belgians (19%) identify as atheists, as do 16% in Denmark, 15% in France and 14% in the Netherlands and Sweden and a staggering 25% in the Czech Republic.
3. Most Americans (56%) say it is not necessary to believe in God to be moral, while 42% say belief in God is essential to have good values.
4. The stronger the religious belief among the citizens, the weaker the country's GDP and Per capita income.
These above facts and similar trends suggest that religiosity is in steady decline. Another such evidence as to how strongly the idea of atheism is spreading is given by the fact that the book 'The God Delusion' by Richard Dawkins has been downloaded more than 3 million times in Saudi Arabia, one of the most religious countries in the planet.
Such observations are strong indicators of the widespread impact of secular principles and the constant remodelling of the moral and ethical compass of human beings as a species. Though it would be quite unnatural to say that the technological advancements would wipe out the religious beliefs from the world, it seems plausible to expect a gradual decline in the religious dogmas as the world moves on to the next phases of the technological revolution. Nevertheless, belief systems will always be there. It is altogether a different thing that these beliefs will be more rationally brought into existence by the advent of modern scientific understanding rather than ignorance and traditional conventionality.
See Robert Sapolsky's lectures here:
See the Pew Survey research on global trends on atheism:
About Richard Dawkin's The God Delusion: