Apart from the well known long-term “heat-death” describing a gradual end to the universe, it has been postulated the more abrupt possibility that the quantum vacuum might only be in a quasi-stable state, and that its reversion to a stable state would set about a radical restructuring of the laws of physics which spreads at the speed of light from source of its reversion – this would cause the end of chemistry, and therefore life, as we know it.
Now a new proposal for an abrupt end has been published. This involves some obscure quantum physics which predicts the ‘instanton’ – a kind of bubble in the Higgs field, which would expand at the speed of light, swallowing everything. However their calculations suggest that this would happen on average once every 10^100 years! (present age of the universe is only 10^14 years)