We have spent considerable time in closed beta testing, and we feel the stability of the build is now very solid. That's why we would like to invite everybody in our fanbase for the final check. Hopefully, if things prove solid under such a scrutiny, the final official retail/Steam update may only be hours or at worst days away from us.
The 1.9 update is one of the largest patches we have ever worked on, hence the long time to wrap it up. Work on the new vehicle AI code has actually started even before ETS2 was released, some year and a half ago, but we gave it all the time it needed to mature. It replaces the entire traffic AI code with a new system. Its far more flexible, and it is paving the way for yet more improvements in the future (country-specific behavior of traffic lights is a much needed planned feature for the future for example).