Some good observations from Andrew Perriman (The Coming of the Son of Man, pp. 83-86) on the “age to come” in New Testament thought.
The word aion occurs most frequently in biblical Greek in such phrases as eis ton aiona (“for the age”), eis tous aionas (“for the ages”), or more emphatically eis ton aiona tou aionos (“for the age of the age”). The meaning of these expressions is simply “forever” – but “forever” conceived as an unending extension of some particular historical circumstance, not as “eternity,” which carries with it the clear connotation of time beyond death or beyond history. To give a mundane example: in the law of Moses, if a Hebrew slave chose not to be freed after six years, his master would bore his ear with an awl, and he would serve him eis ton aiona – not for eternity, but for life (Exod. 21:6 LXX). The adjective aionios is used in the same way…
If the “age to come” is the age that follows the collapse of Second Temple Judaism, what are we to understand by the phrase zoe aionios? Instinctively, we read this as a reference to “eternal life” with God in heaven, but as we work through this material, we find ourselves increasingly blown by the winds of interpretation in the direction of a more realistic and “worldly” understanding. When Jesus promises his followers that they will inherit the “life of the age,” he must mean the life that will be experienced by the people of God following the climax at the end of the age, following the judgment on Israel [in A.D. 70 – ATR], the life that will last throughout the age which is to come – and which has now come. It is the life in the Spirit that is given to the people of God following suffering, death, and resurrection (cf. Dan. 12:2).
To summarize: the “age to come” is the age that we now live in, the age of the eschatological Church and her reign on the earth which the Old Testament saints expected and waited patiently for and which Jesus and the New Testament apostles expected to arrive within a generation of the time of their ministries. This is about material, physical life dwelling in the light of the Spirit, experiencing the life of the Spirit in the gathered people of God, the Church.
This is not to say that there will not be a final judgment and a physical return of Christ at some point in our future, as Perriman emphatically argues – rather, it means that our understanding of the New Testament, the eschatological bits of Isaiah and the other prophets, and the later parts of Revelation in a new light as being present now on earth in the form of the Church, and one day in literal fullness at some future point in history. Jesus and the apostles spoke of the beginning of the “age to come.” They rarely have any interest in questions as far distant as a final judgment of all history many thousands of years in their future.