BTW, I think that 1 is all but ruled out (and 2 is slightly disfavoured) by the failure of SETI (at least if you interpret the present tense to mean ‘as of the time their wordline intersects the surface of our past light cone’), and 5 is unlikely because of Moloch (if he's scary enough to stop cancer from killing whales he's totally likely to be scary enough to stop > 99.9% of civilizations with supercomputers from taking over the light cone).

My own probability distribution has a broad peak somewhere around 4 with a long-ish tail to the left.