1. We may live in eco-friendly houses in the future. They may use advanced technology to produce light and warmth.
2. I think global warming get worse and there may/might be more natural disasters.
3. In the future, our school might buy a lot more new computers and then we may use the Internet to find out information.
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May/might могут быть использованы как в настоящем, так и в прошедшем времени. Чаще всего may употребляют в настоящем времени, а might, как глагол, в прошедшем.