The sun will become more luminous to a point it will stop plate tectonics by evaporating the oceans far sooner (about a billion years from now) than it will take the earth's core to cool.

By that time we will have completely different issues, like enlarged sun burning everything down

We’d be in the sun

Not immediately. We'll see it coming, but quarterly corporate plans and 4-5 year election cycles will mean we won't do anything until it's too late.