Could the universe end while we are alive?

Probably not. Based on current physics, it is extremely unlikely that the universe would end during our lifetimes.

The main ideas scientists discuss for the universe’s long-term fate happen on timescales far beyond a human lifespan. One common scenario is continued expansion and cooling over immense stretches of time. Other possibilities, like a Big Rip, are speculative and would not be expected anytime soon under current models.

There is one theoretical exception: vacuum decay, a hypothetical quantum event in which a new vacuum state could form and spread at nearly the speed of light. In principle, that could happen without warning, but there is no evidence that it is likely, and it is generally considered extraordinarily improbable.

Also, the Sun will become a red giant in about 5 billion years, which would end Earth as a habitable world long before the universe itself ends.