Everyone who believes in Christ has been born of God. Belief is not confined only to the present. You can still believe a second, a month, a decade ago. You can even believe into the future.Dr. Rob Plummer is a Greek scholar. He's written a grammar, he teaches Greek, and he has a daily video called, "Daily Dose of Greek", where he spends a couple of minutes each day parsing and translating a verse of the New Testament each day.
He's already gone through 1 John, and the page with the 1 John 5 verses translated can be found here:
1 John 5 Greek Readings | Daily Dose of GreekIn an effort to help you master New Testament Greek, we read 1 John 5 in one 2-minute video per verse. Enjoy!dailydoseofgreek.com
Since his videos are intended to help keep students' translating skills sharp, he concentrates more on translation, but he does occasionally refer to interpretational nuances as they appear. As he translates "γεγεννηται" ("has been born"), he points out that it is in the perfect passive indicative, and contrasts that with "every one who is believing" being in the present tense.
In fact, at the one minute mark he states:
"Notice the shift in tenses here. We have the present, the person who believes, who evidences current belief, HAS been born, perfect tense, from God."
So Dr. Plummer thinks the shift in tenses (from completed past action, to present tense) is significant here. Further, he points out that "has been born" is passive, it is not something we do, it is something done to us.
Therefore in this discussion, the tenses are not as significant as to what is the cause and what is the effect. Whoever believes is born of God. Here, the cause is clearly belief and the effect is born of God. Belief precedes birth.