I try not to talk about these things too often, but Stephen Hawking, speaking loosely and probably after knocking back one-too-many, has publicly suggested the possibility of time travel. He reaffirms that travel into the past is impossible, so there's no need to quibble on that point. However, he posits the potential to travel forward, relying on Einstein's theory that objects nearing the speed of light progress through time at a "relatively" slower rate than objects on Earth. That is, a person moving at 98% of the speed of light for 20 years would find the Earth had "aged" 7,500 years.
Yet this is not due to a traveler having stepped outside a "stream" of time and reinserting himself in an extant, "future" age already in place and waiting to be discovered. Rather, in accordance with static theories of time as a non-progressive measurement of "aging," it simply reveals the unified application of time's effect on various objects in a consistent manner, according to their relative conditions (i.e., speed). So, there is no future world (or infinite worlds) already in place, merely awaiting our arrival. Time is simply the observation of material entropy and the extinction of potential possibilities (i.e., thoughts and actions) through the free-willed choice of particular decisions during a single, ever-present moment.
Steve is so sloppy about these things sometimes.