The stars will burn out and suck in all propulsion when they become trillions of trillions of black holes. Yeah, there probably is a large black hole where the big bang happened, where everything is expanding away from, we obviously can't see it. All forms of energy have gravity, light bends around the gravity of a large object or large mass. The light travelling out at the furthest part of the universe would be starting to turn around, like a bullet fired in air, turning in orbit of the gravity of the universe, or random large objects and galaxies behind it. The universe is currently expanding faster now, but when the stars burn out, hot turns cold, and what goes up, must come down. Nobody can prove or disprove this theory, the big bounce theory, they don't even know what dark energy is, and likely won't be able to work out what it is, ever.