Original GitHub data is for 2012 - 2020. Rest of the data is extrapolated using linear regression. Programming languages move slowly, so my future prediction has a decent chance of holding.<p>I will try predicting further into the future via introducing seasonality and using a more complex extrapolation formula. We'll see how it goes then.
Update: 2019 Q4 Python data is an extrapolation error. It doesn't swing up enough to surpass JavaScript. Though it might by 2023, that is yet to be seen.