I reckon someone alive today will be alive in 1000 years time. Not everyone, but at least someone.
The method would be to largely avoid decaying organic matter by replacing an increasing amount of our aging bodies with artificial parts that are more reliable, maintainable, and (eventually) easily replaceable.
Within the next 100 years all essential organs will be replaceable with technological equivilants that are generally serviceable, including skin. Maybe this will still be expensive and unreliable but it will add a significant amount of life to someone's life.
There will be further enhancements to this utilising an increasingly sophisticated technological casing that becomes increasingly reliable and greatly enhances human life in all aspects.
As time goes on we will find new ways of efficiently nourishing the human brain and maintaining it in its healthiest state.
Eventually we will find a theoretical permanence for the brain. Maybe someone alive today will be among those who witness this. It's hard to imagine a mind from today's world reaching a stage of theoretical permanence, but who knows?
