It is now five years since the discussion started, and there are no clear timeline or scuccessfactor. I have asked in phab:T137282, but it is declined with no further information. I conclude that the project is stalled.
Topic on Extension talk:Gadgets/Gadgets 2.0
Five year old project
The project is not stalled, the Phabricator task was only declined because deadlines do not help anyone.
There are virtually no information available about deadlines and progress, that is why I conclude that the project is stalled, not that the task is closed. It is also somewhat weird that WMF strongly stresses use of success indicators, and at the same time there are projects with no indicators at all.
Progress is happening slowly. For the most part, this isn't an officially resourced WMF project anymore, it's just something that developers are doing in their spare time, which is why it's pretty slow. Community Tech has also helped push it forwards a bit.