If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe, closing the Mediterranean, Australia will collide with S.E. Asia and California will slide northward up the coast to Alaska.
Though there is no way of knowing what the future geography of the Earth will be (except maybe through our friends at the Psychic Connection), it is possible to project current plate motions into the future and make an educated guess. In general, the Atlantic and Indian Oceans will continue to widen until new subduction zones bring the continents back together, forming a Future Pangaea.
The world 50 million years in the future looks slightly askew. North America is rotated slightly counter-clockwise; Eurasia is rotated clockwise bringing England closer to the North Pole and Siberia southward towards warm, subtropical latitudes.
Africa will collide with Europe and Arabia closing the Mediterranean Sea and the Red Sea. A Himalayan-scale mountain range will extend from Spain, across Southern Europe, through the Mideast and into Asia. Similarly, Australia will beach itself on the doorstep of Southeast Asia and a new subduction zone encircles Australia and extends westward across the Central Indian Ocean. It is interesting to note that present plate trajectories suggest that the East African Rift will not grow into a wide ocean.
One of the most important changes in the geography of the Future, is the beginning of subduction along the eastern coasts of North America and South America. Though the Atlantic Ocean has widened, the Puerto Rican Trough and Scotia Arc may propagate northward and southward along the east coast of North and South America. In time, this new westward dipping subduction zone will consume the Atlantic Ocean.