Here is the roadmap for the next update. (Was scheduled For Release 2018-11-01) but problems kept it from being released.
They are at about 72% done.
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Take it with a grain of salt, though. New issues get constantly assigned to that target version as we discover them and decide to fix them in the next release. So the percentage may not move as noticeable as the scope increases.
Other issues that are currently assigned to the version may not actually seem that important to fix, are just difficult to reproduce in general, are already fixed for the most part and just not resolved completely, or simply are not something I'd actually consider a bug. So issues might be removed from the target again.
There is also a lot of work being done that's not directly reflected in the roadmap. Often we just go ahead and implement something without explicitly creating an issue for it.
I've also done quite a bit of work on the planned modding framework, which I'd consider about 70% done right now. Most of the remaining work is UI stuff, which sometimes really can be a PITA.
That's in a separate development branch, though. It won't be included in the next 1.9.x release, since I'd like to deliver a proper stable release first. The modding framework changes how the engine handles resources under the hood, so there is more chance for things to go awry at first. It's planned for 1.10, which hopefully will take much less time to be released after 1.9.x is out. The goal is to have smaller and more manageable releases after the modding framework.
One thing that was kinda needed for the modding framework are proper global variables, so that will already be included in the next 1.9.x release to give event authors some time to migrate to the new system.
As for 1.9.x, it's pretty much ready on the programming side of things. Just waiting for Spinner to finish up his work on the event side. Then the game will go into beta testing phase (probably for a couple of weeks) before the official release.