The last big game mechanic being added is storage - basically, a mechanism to cap how many resources you can have at once. Every type of resource besides gold is now capped, so you can't accumulate a massive surplus without building the infrastructure to actually hold it. "Infrastructure" is an overstatement in some cases though, for wood and stone it's just an empty patch of dirt:

Other resources have something a bit more substantial, such as a grain silo or a warehouse:

Some resources are only unlocked in later progression levels. For example, coal can only be mined in level 2 and later. The storage buildings for these goods will only be built once the resource has been unlocked, then a "free" instance will be built. (Free being in quotation marks because you already paid a substantial upgrade fee.)

Additional storage buildings can be built later - as of now, they are all available in level 2 for the massive cost of... 1 gold. The costs will definitely be balanced in the future, and you'll notice some missing icons, but I figured I'd rather keep a barely-implemented feature than lock the player into a very small resource capacity.

A neat side effect of this is now there's kind of a job priority system for your pops. A resource producing building cannot complete its work until there is free storage space available, and if it waits too long it will kick out its workers and block any new ones from coming in. If you happen to have more jobs than pops (or too many of them are sleeping), this is pretty helpful - now the pops won't waste their time trying to pump more water if you've already filled your tank to the very top.

I'm in the midst of testing the "Alpha 1" (0.5.01) build of Iron Village on all the platforms (Windows, MacOS, Linux, Android), but here's the full release notes since 0.4.03:

• Pops now have "Satisfaction" values, which is affected by their housing status.
  • Sleeping in an actual home increases this, sleeping in a train station decreases it.
  • Being assigned a home increases this value, being evicted has a dramatic negative impact.
• Pops with a low enough satisfaction value will wait at the train station for the next passenger train, and then depart.
• Pops who are experiencing homelessness or are waiting to leave will display an icon above their head showing this information.
• Wells have had their production time doubled, i.e. the rate of production has been halved.
• Fuel requests from trains can be marked as "auto" on a per-resource basis via a checkbox. When checked, trains will try to automatically take as much fuel as they need without further player input.
• Resource buildings will not restart production until they can successfully store their output.
• Added a bunch of different storage buildings as described in the dev diary above.

• A small countdown clock appears while a train is stopped at the station.
• Pops will not try and work a job if the building is waiting to deposit its output.
• The first train only carries 3 passengers instead of 4, so that they can all be housed more easily.

• Trade UI updates and fixes, including:
  • Quantity displayed resets to 0 after a trade is done.
  • Capacity of the train car is actually respected
  • Max and Min buttons added - reset to zero, or fill as much as possible with one click.
  • Graphical refresh
• When levelling up in progression, certain new buildings will be built.
• Resources now have a capacity, although in certain cases (Gold) it is effectively infinite and not displayed.
• Game speed can now be controlled by the keyboard: Space or P to toggle pause, 1 for playing at 1x speed, 2 for 2x speed, and 3 or 4 for 4x speed.
• Minor graphics tweak for building costs that are three different resources to fit it within the button.
• Certain demolition jobs (just trees at this point) actually require sending a pop. These jobs yield resources only at completion.