I questioned Birken today, and this is what he said about what optimizations you can expect in 1.4.
Map optimization
Loading times optimization
Interface optimizations
Optimizes to timeflow
Fixed crashes
Also, good new to modders!
This is not a complete list obviously, but it should give you an idea regarding the optimizations that have been made.
Map optimization
The memory usage of the map has been optimized and now has approximately 60% of the memory footprint.
Loading times optimization
The map now loads quicker due to the smaller size and restructuring of the map data. The loading of map textures and tree creation time have also been made faster.
Interface optimizations
The split unit stack interface is now faster.
Production screen loads quicker.
Optimizes to timeflow
Lots of optimizations in the AI to handle large troop sizes better.
General optimizations in the daily tick.
GUI render loop has been optimized.
Optimized border updates, fixed bug that messed up borders in some cases.
Fixed crashes
He is being modest here. I know for a fact that he has fixed more crashes than this. A nasty crash during start-up that was introduced in 1.3 for example.Fixed some crashes related to the surrender and annexation of countries (i.e. Vichy-event crash ).
Also, good new to modders!
New DateTrigger that can trigger on a given day (NOT hour) "date = 1938.3.1".
This is not a complete list obviously, but it should give you an idea regarding the optimizations that have been made.