The Dandelion Universe
So we don't all live on a yellow submarine.
We live in a universe which rapidly inflated from a 'nothingness' and expanded into the universe we observe today, a place filled with the visible matter and a lot of dark matter (and dark energy) contained within the cosmic event horizon.
And though for a while we may have thought the expansion of the universe was contained by gravity and/or a sort of surface tension of the outer rim (skin) or cosmic event horizon, it now seems that the universe may still be expanding and even accelerating - perhaps taking the shape of the spiral galaxies we observe, including our own home the Milky Way
And yes it is possible that anything on the outer limits may accelerate and reach the speed of light, or even fall outside (escape) the cosmic event horizon. Of course this may already have happened to some of the original universe. We would be unable to tell, since we cannot see beyond the event horizon.
These things occur on a cosmological time-scale, so it is not easy for us to see in a human life-time. In the mean time we amuse ourselves trying to speculate, theorize and debate what may have occurred billions of years ago, and what may be the consequences now & today billions of light years away.
Testing Einstein: Is Dark Energy Constant? - CfA Press Release
Major Step Toward Knowing Origin of Cosmic Rays - from NASA
Stellar Explosion Outshines Sun 100 Billion Times @ Live Science
Orion Measurements Change Stellar Distances - Centauri Dreams