Here's the likelihood of McDavid reaching 150 points (assuming he plays all 82 games), updated after each game:
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"0" is the probability before the start of the season (around 7%). The low point was in late October, when McDavid "only" had 11 points in 7 games. The high point was mid December, when McDavid had 59 points in 30 games.
My model gives him virtually 100% chance of reaching 120, 95% chance of reaching 130, 69% chance of reaching 140, and a 4% chance of reaching 160.
For those curious about goals specifically - McDavid has a 92% chance of scoring 50 goals and a 29% chance of scoring 60 goals.