Im expecting the PS4 to do like 16m in 2019.
That ontop of the 91.6m should mean early 2020 the PS4 will be at ~108m.
2019 is the year the PS4 overtakes the Wii & PS1 and becomes the 2nd best selling home console of all time (DS+gameboy are handhelds).
Number of days to reach 50M from 40M : 198 days
Number of days to reach 60M from 50M : 187 days
Number of days to reach 70M from 60M : 175 days
Number of days to reach 80M from 70M : 227 days
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249