Special Note: Please note that this scenario is meant to be read as entertainment, not as an accurate prediction of the future. Also note that the viewpoints and opinions that may come across in this scenario are not necessarily the viewpoints and opinions of the author.
As much as human beings would like to admit that they will live on the Earth until the sun dies out in the year 10,000,000,000 A.D., someday they will have to leave the planet to explore the cosmos.
Humans are currently abandoning religious studies in favor of scientific knowledge as to learn the skills need to colonize other planets and prosper on them. Converting from an organized religion (Christianity, Judaism, Islam, etc.) to atheism is a lot like leaving your parents' house forever. You get to set your own standards to live life. It was already proved by 90% of the global scientific community that a Big Bang Theory was caused by a serious of astrological events with no God-like being to start it. The drive to get people away from organized religion and into science has caused the declining church attendance figures of the 21st century and the rising interest in science-oriented websites like YouTube, Wikipedia and Future Wiki.
Under human rule
Around the year 4000 A.D., the Earth will be relegated to a status of the center of an intergalactic republic (with natural goods in permanent abundance thanks to nanotechnology). Once considered the only inhabitable planet of the universe, it became just one of many civilized planets by the year 2105. The Earth houses only government workers (who have to work on planet Earth), naturalists (who admire planet Earth), environmentalists (who want to help planet Earth), tradespeople (who work the high-tech green jobs on planet Earth), merchants (who have to import and export stuff like food, water, electronics, and other essentials), and conservatives (who find living on a space colony to be disgusting).
As the center of the Terran Intergalactic Empire, the planet once called the "only planet we have" is subjected heavily to diplomacy meetings and intergovernmental conventions between humans and extraterrestrials. Pollution will have long been neutralized by nanobots along with climate change, global warming, and carbon production. A vegan diet will be mandatory for all humanoid units that can safely consume solid food. The humans will plan their final exodus some time before the next Ice Age due in the year 25,000 A.D. and people will abandon the Earth for a while. Other animals evolve from our present day animals leading to a sapient race of insects 200 million years later.
By the year 9,500,000,000 A.D., the sun will be so hot that not even amoeba will be able to live on Earth. Humans will have long since abandoned this part of the multiverse and will have colonized a nearly infinite amount of universes and galaxies.
Under insect rule
A group of insects which evolved from modern termites evolve into a civilization with cities vaguely resembling those of Bronze Age human civilizations in the year 200,000,000 AD. Algae (food) will be herded from nearby desert creatures and water will be found deep underground in caves.
Humans will have evolved into a non-corporeal form using mainly pure digital energy "souls" instead of human or cyborg "bodies;" leaving behind a mass network of "old-style" urban cities and "post-modern" arcologies behind. Unlike the human civilization of the future, this civilization will have many castes, and the ideal conditions to develop a stable democracy or even to form religions are unlikely to develop as scientific progress is greatly delayed due to an excess amount of workers and an exceedingly small amount of intellectuals and aristocracy.
Insects tend to rule with an absolute monarchy, and sentient insects will most likely be no exception. Someday, maybe insects will see this when exploring ruins of the civilization that the "giant humans" once inhabitated when they were dependent on a physical body for breathing, eating, drinking, and living in general. They will find the letters much too big to read with their little insect eyes, but they will create a Rosetta Stone to translate this message into their little insect language. Gradually, they will increase in size and follow humanities footsteps and be ruled by a totalitarian dictatorship similiar to that of the 1968 classic movie Planet of the Apes. After developing the ability to colonize other planets in the year 850,000,000 A.D. (insect science is very slow compared to human science), the insects finally leave the Earth and never return.