The basic idea with the future and Christianity is that there will be a fully divinely infused society, where people have ‘glorified’ bodies. You could call this the grand vision of Christianity.
Glorified is a theological term, but what it translates into is bodies that are full of health, and aren’t programmed to die at a specific point, i.e., immortality. It is important to note that Heaven in Christianity isn’t about a disembodied existence (Heaven is full of people who are fully embodied, physical) and that Christianity posits this occurs through reincarnation (that is, a person becoming bodily again).
(This leads to the question, is reincarnation plausible? The problem is that we don’t understand incarnation, much less reincarnation. That is, why am I ‘in’ this body, or similarly, why am I ‘in’ this body while you’re ‘in’ that one. It is not enough to equate the subject ‘I’ in these cases (and corresponding subjective experiencer) with the stuff of the body, as this changes throughout one’s life. It is also not enough to equate it with specific functioning, as this also changes throughout one’s life. So, we don’t really know how to answer this question within a standard, ‘physicalist’ framework, at this point.)
So, the purpose of this life, as far as it relates to God’s purpose for us according to Christianity, is to a) move towards theosis oneself, and b) to help to bring about this future society which is fully divinely infused (theosis in a broader sense) and in which humans are full of health and immortal (‘glorified’).
One interesting aspect of recent history is that, as we have moved closer to something like ‘glorified’ human bodies with contemporary technological breakthroughs, we have simultaneously moved away from Christianity – even though Christianity predicts this is what will happen.