I didn't interpret the results in this post as "predicting the future distribution of language use." Rather, I interpreted the ranking as an indicator of a qualitative trend in that distribution. I think the author also made this very clear.
And of course, all things trend toward newness, so your objection there seems more about time or human psychology than the methodology of the post.
Nevertheless, it seems quite obvious the author did not literally interpret the eigenvector as "x% of future projects will be written in Go." Rather, the conclusions he drew were along the lines of "Oh wow look Go is on top, C and Java are still relevant."
I reserve the right to respond to what people say. Commenting on the accuracy of a label is worthwhile regardless of whether the label was meant to be precise or loose.
And of course, all things trend toward newness, so your objection there seems more about time or human psychology than the methodology of the post.