What I'm saying is not directly related to your data request but to your comment above:

We've been working on a project to understand gaps in Wikipedia and increase content coverage. You can read more about it here. As part of the project, we are developing a tool that will provide article recommendations (for translation or creation from scratch) based on articles available in a source language x and missing in a destination language y and the user's interest model. You can check out the current state of the tool here (note that the tool is not ready for public consumption, yet.). The phab tickets for the tool are here. :-). You can read more about the tool here. This project can help those who are interested in recommendations to receive recommendations about what articles can be created next in their local language.

Your question about tracking the change in language versions while reading the article is definitely interesting for us given that it can be used as a signal of demand in the destination language.

Best,

Leila