It depends on your target frame rate and the available hardware at the release date. In it's current state, it runs at 22-35 fps on a Nexus 4 and that includes sound, path finding, ai and collision detection for the player, projectiles and enemies. Given that a release is still in the far future and that i consider 25 fps to be good enough for a RPG, i don't see any real performance problems. If nothing else helps (on low end devices for example) i can scale it down by reducing the amount of grass patches.