It seems like your heart is in the right place but the quoted statement reads to me as a total non-sequitur. What model are you using to justify your calls for GitHub to hire 9x it's current number of employees?
What would these 4.5K new employees be doing exactly?
At the end of the day they provide a useful way to store and version control a code base, but the enterprise software market is very crowded and GitHub being in vogue could be a fad that gets eclipsed by something else, just like how HipChat was THE thing for teams until Slack.
Arbitrarily saying that "Google will birth AI and they need at least 1M employees to make it happen" is something that, in my opinion, sounds similarly vapid from any kind of quantitative or forecasting standpoint.
Would like to know how the figure was estimated, and how mentioning Yahoo is relevant in the least. They have a huge stake in Alibaba, and yahoos business model is a defacto investment company, with Yahoo standalone value [yhoo market cap - (yhoo stake in baba)*(market cap of baba)] around -15B last I checked. It's not even apples and oranges, it's like grapes vs dolphins - meaningless comparison
Edit: fixed my yhoo/baba math for clarity