@redfrog It depends what you call "current trajectory", but with the current policies the warming is projected to be 3°C. https://climateactiontracker.org/global/temperatures/
There is naturally a range of possibilities around this 3°C and we do not know whether countries will stick to their policies. So it is hard to say which trajectory we are on.
I am not aware of a reliable scientific source claiming to know when civilization or humanity goes down.