As I have reflected over the phrase translated as "eternal life" (ZWH AIWNIOS), I am strongly inclined to agree with the note N. T. Wright makes in The Climax of the Covenant, p39n77, "I regard ZWH AIWNIOS as denoting not just indefinite continuing existence after death but the now-inaugurated 'age to come' of Jewish eschatalogical expectation"
Similarly, Don Carson notes in his commentary, The Gospel According to John, regarding the phrase in John 3:15, pp202f, "Properly it means 'life of the age (aion) to come' and therefore resurrection life. But in John's Gospel that life may in some measure be experienced before the end, just as in the Synoptics the kingdom dawns before the end. Moreover, those who have read the Prologue will recall that life resides in the Word: 'in him was life' (1:4). The eternal life begun by the new birth is nothing less than the eternal life of the eternal Word."