A-Z of the Future > Oblivion
There a number of scenarios modelled by astrophysicists which culminate in inert meaninglessness as far as humans are concerned. From the Big Crunch to the Big Chill (the dissipation of all energy), they indicate the universe will die and all trace of our existence will go with it.
It's not just humanity, but the universe that is mortal. Perhaps though this can galvanise humanity or even provide legitimacy for humankind’s Promethan aims. Should we allow good and evil to have no ultimate meaning on the cosmic scale? Or should the ultimate aim of humanity be to stave off the death of the universe, perhaps create new universes? Could artificial cosmogenesis play a role in making the universe itself immortal or replaceable? It should be noted though that all this is just theory.
Our universe may just be one of many multiverses, some have even argued we ourselves are an example of artificial cosmogenesis - that we are a computer simulation. What this seems to suggest is at the deepest metaphysical level we still understand very little about the nature of reality.
There's also an ever expanding host of existential threats facing humanity. Perhaps this last point dictates that our aims should be directed to preventing our own oblivion and that of the universe at large. We have a few billion years to deal with the bigger problem of entropy.