I don't really understand why this is a question. Topics like this always seem like a false dichotomy to me.
We fill the gaps with actual experience and finding meaning and ongoing stories about that in the form of culture. This is what we do and have done and will continue to do.
Just because we label aspects of our misbeliefs and myths (as in lies about reality and as in symbols) and social structures "religion" doesn't actually indicate a real line there. We still engage the world in terms of group identity, personal identity, beliefs, experiences, and assumptions, etc. With or without organized religion, we still ask questions about existence and others will still try to answer them and we will still fall prey to fear, ignorance, pleasure seeking, ego, bias, and all manner of cognitive distortions. Out of some of this group activity arises systems we call religion.
Even within organized religion, it's all pretty much anarchy, just like everywhere. No two heads are alike in the mental framework of beliefs about what the world looks like or should look like. No matter how much anyone wants to insist that their beliefs don't change and that they are uniform across the members of the denomination, this is not the case at all. Mental realities and belief systems will continue to change and morph and sometimes collapse with ongoing experiences. Holding the delusion that our stories and artifacts are the source of our conscience, goodness, security, "civility" or our very existence doesn't actually make it true. All of our ideologies and history combined can't change that. They can impinge back on us and reshape our entire life stories - and the ongoing conversations about how religion impinges on human minds and groups help us to possibly shape ourselves into something better moving forward - but they are not the source of our decisions or experiences or happiness or understanding. However, it's easy to understand why even suggesting this might be frightening to a lot of people under such a delusion.
Already our world views incorporate the entire earth, all cultures, all life on the planet, and even possible life on other planets. Everyone's world view must change to accommodate new imagery and knowledge, whether they like the new information or not, it must be incorporated in some way. What we call religion is really just a picture of our understanding of the world at certain places and times, mashed together over centuries, and spread to others all while the belief system is squished and filtered and bent through culture after culture and through other belief systems. But we tend to only call it religion when it involves claims of absolute truth or an unchanging nature.
So perhaps what might be "replacing religion," i.e., what is changing in our cultures and behavior, is exactly what we see when we look around the world right now - the same thing it's always been: stuff we knew before getting mixed with stuff we learn as we go and us telling stories about it.
