That would be true if the sprite origin was at the center. In the event that it isn't the following will do it
tk2dSprite sprite;
var bounds = sprite.GetUntrimmedBounds();
target.position = sprite.transform.position + new Vector3(bounds.center.x + bounds.extents.x, 0, 0);
Use GetUntrimmedBounds if you want the full bounds of the source texture, use GetBounds if you only care about the visible data.