This is a big question, deciding the destiny of over 9 billion people who will be living on earth when oil is finished.
Oil (here it refers to both, oil and gas), is being used by us in tens of applications, equipment and systems, such as in our cars, clothes, planes, ships, electronics and many others. We need oil, either as a source of energy, or to make things we need every day, like plastics. With the development of alternative energy sources, the world started switching slowly to these, which though still represent a tiny percentage of energy coming from oil, it is increasing exponentially. After oil, some of these new energy sources, like solar, nuclear and others, will be sufficient to replace oil, in some of its usages. A good example is, road transportation, rail services and for generation of electricity.
Unfortunately, there are still many other usages and applications of oil, where these alternative sources are not adequate to replace oil, and some of these are critical to our life, such as aviation, shipping and for producing plastics. Planes driven by batteries, solar energy or by hydrogen fuel, still not proven or ready as a viable techno commercial option. To make them feasible, a huge leap in the development of the battery technology is needed, so it can store at least 70 times more energy in its current size and weight. Electric planes will never materialize and become feasible without this achievement. Using hydrogen, though being investigated, still not proven techno commercially, plus pauses several challenges, related to hydrogen handling such as, production, usage, transportation and management. Same challenges apply to shipping services. Though one option may seem feasible by using a technology called the Miniature Nuclear Reactors (MNR) on very large ships and planes, still has many challenges and obstacles, related to security and safety issues, since you need to move a nuclear reactor around, in the oceans and air, driven and used by normal civilian people.
Plastics represent the other big challenge after oil, since without oil there will be no plastics. Imagine our life without plastics, which is part of almost every thing we do or use, like clothes, furniture, cars, electronics, computers, pipes, wires, etc… the argument of using biopolymers to produce plastics (plastics from plants) is a big myth, since the world is already having a food crisis and by that time it will be much worse.
So, can you imagine the world without aviation, shipping and plastics!!!
Is it a livable world?
May be, if people at the time accept to turn the clock back by 140 years, accepting to live like their great grand parents.