The positions of the planets in our solar system have been predicted for about the next 1 billion years and there is no sign that they will ever stray from their current elliptical orbits. We cannot forecast, however, whether some passing star might stumble by in 100 million years from now and upset the current planetary orbits. We do not know of any stars that are within 100 light years or so of the Sun which are on a collision course right now, but interstellar 'billiards' is a very complicated game when we do not know enough about our neighborhood in the Milky Way.