Future is simple more polygons and bounced light.
So I've made such kind of scene in Unity where trees not a crazy plane monsters...
I think we should leave faked graphics like bill boarding and came to full polygonal graphics with realtime bounced light model in games, This tress contain every pin on their own polygon. With such scene I can navigate with ok fps in Unity
Some additional resources.
DOWNLOAD pinetree 3D model used in benchmark:
Unity 5 is very promising in terms of creating cool physics based lighting. So I've made a quick test of SpeedTree support and got this: