Why wonder - why not just look it up? https://www.edsm.net/en/expeditions/summary/id/58/name/Distant+Worlds+2+-+A+Voyage+of+Discovery
Looks like around 30% made it to the last waypoint (not much point looking at this week yet as many will be taking the info about being closest to Colonia and heading there first, I know that's where I am). ofc it seems only about 50% bother to upload their tracks, but they are probably the more dedicated / organised explorers, so it's likely less than 30% of the total.
(And that drop-off seems typical for exploration trips, other expeditions see the same pattern)
Is this automatically updated when I reach each waypoint?