I doubt there will be new content. It's not worth the effort working on jmonkey Java engine. Better use the resources for unity.
The plugin planks and beams works like a charm and meets your first demand though. To not break immersion you can define costs of wood, metal, wood, etc to buy the planks, beams etc you want.
New plants won't be added. I'm pretty sure of that.
Auto pickup neither i guess. But honestly, resources ingame are plentiful. I usually just destroy stuff i don't want anymore.