Progress on siunitx version 2 has not been as fast as I’d like. There are a few reasons. First, my “TeX time” has been squeezed since the start of the year as I’m doind a couple of Open University courses. Some of the “TeX time” I do have has also been taken up with jobs for UK-TUG, mainly the website and membership renewals. Finally, when I looked at the wish-list for version 2 it turned out to be rather more complex than I’d remembered!
The net result is that I need to revise my initial timetable. I’m still aiming for release before the end of the year, so I’d like to get a testing version finished by early autumn (late September or early October). My key aim is to get some internal structures improved, so that I can build new features over time (even if not everything makes version 2.0).