WE haven't got nuclear fusion. Nobody knows whether we ever will have it, and whether it'll be possible without all kinds of unfrtunate side-effects we don't know about yet.
Depending on that to sort our problems out is like counting on winning the lottery to pay this winter's fuel bills, and stop the rain coming through the roof.
The technology that would help is there in principle already, far closer to being developed than nuclear fission. But market forces can only start to bite when the costs using fossil fuel get high enough to make it profitable to turn to other ways instead. And most of the increasing costs of burning fossil fuel are falling on people who have no financial or political power. We have to pay a bit more for petrol. They die.
And I'm afraid that is a situation which is bound to produce the most terrible things. "Natural" disasters and conflicts in the poor countries, escalating terrorist outrages in the rich ones.
The only hope for things getting better will be if enough people who do have economic and political power determine to use it to turn things around. Which might sound like altruism, but it's really just enlightened self interest.
How's it go? "On the 31st floor your gold-plated door won't keep out the Lord's burning rain."