100 years is quite short as there are still a ton of religious believers and tradition is stronger than you think. But with the recent technological advances that allow free movement of thoughts and ideas, theism will certainly be trending sharply downward over the next 1000 years, should humans make it that far. Short term, humans are in a pretty difficult position actually. Nationalism, conflict of religions, resource depletion, exponential population growth and demand, global climate change, etc are all going to be massive challenges and humans may struggle or may never get the answers so believe in God to rescue us from these dilemmas will not likely change.
Also death is a big obstacle. As long as people realize there life is about to end, they are going to look for something else.