I don't think really that a majority of the population is going to die. I do think significant numbers of deaths will happen around the equator at some point in the near future and spark a functionally unstoppable wave of immigration towards the earth's poles. This will result in its own strife but again will only cause a small percentage of more of the population to die.

Thing's will eventually stabilize as human civilization adapts and green energy and carbon capture take off. Most of the population will survive but almost everyone's QoL will be NOTABLY worse by various conventional metrics. Though likely better in specific ways due to certain medical and automation advancements.

Expect birthrates to continue to drop globally however and the earth's eco system will drastically change and become much less healthy. Most of existing humanity will cling to life though.