Something of a question mark of how long the tropics are going to remain habitable. We're still on the "business as usual" emissions curve, with no signs of meaningfully changing that. That puts us 5C higher by the century, and will keep going up after that.

Many equatorial regions will either be too hot for human life, (https://advances.sciencemag.org/content/6/19/eaaw1838) or be active combat zones as a result of refugees escaping heat. Some cities in India are now routinely hitting 50C during the summer, and we've only had 1C of warming.

If the tropics threaten to become uninhabitable countries like India will go ahead with direct climate engineering by dispersing fine particles in the stratosphere to reflect sunlight. This need not be at all expensive, even for them. No credible threat from other countries would deter them, as they'd face mass destruction otherwise.