There are two sides to this: a problem and a suggested solution.
People abandoning projects are a real problem. One way to go about it is to give all the people watching it a notice when the repo owner hasn't interacted with the repo in, let's just say, three months.
They could just leave it at that, or they could add a post mortem note with the most popular forks, or call for a vote for the unofficial official replacement repo.
The problem is real, but like you, I don't like the suggested solution all that much.
GitHub would put too much at risk in following such a huge change in its core.
Really, this is a good idea, for a competitor.