New weapons are incoming. I can't add japanese for now. I'm working on operation Overlord. The map is the normandy, i should make a totaly new map for adding japanese troops. DLC with new maps will added only when the main game will complete.
V0.6 (and some other future updates) will be the last free versions. To have access to some future release, you will have to pay the game on itch.io. anyway it will be some few cents.
For the full release on steam it will have a final cost. I think it will not more than 10€. Anyway it will aviable even on itch.io if you has already paid for it while it was in development.