I notice you didn't use any Scriptures to support your position. I did.
That John should use the present tense is what God, the author of Scripture (2 Tim 3:15-16 ESV ), states. You stated: 'There's a difference between knowing one has it and actually being in possession of it'. This is not true in my case. I know I have one Toyota Camry and do you know what? I'm actually in possession of it.
Perhaps we are dealing with two different issues. We can continue to know NOW that we have eternal life (as 1 John 5:13 affirms) and we have the ultimate consummation of eternal life at Christ's second coming.
If you worked today you earned money, correct? However, I'll bet you have to wait until the check is written to obtain that money that is yours. You quoted 2 Tim 3:16, when Paul wrote that the Scriptures were the OT.
I didn't post Scripture because I didn't think it was necessary since by definition eternal life means one won't die and we know Christians die. However, I can post Scripture.
29 So Jesus answered and said, "Assuredly, I say to you, there is no one who has left house or brothers or sisters or father or mother or wife or children or lands, for My sake and the gospel's,
30 "who shall not receive a hundredfold now in this time
-- houses and brothers and sisters and mothers and children and lands, with persecutions-- and in the age to come
, eternal life. (Mar 10:29-30 NKJ)
Jesus said it is in the age to come.
11 But you, O man of God
, flee these things and pursue righteousness, godliness, faith, love, patience, gentleness.
12 Fight the good fight of faith, lay hold on eternal life
, to which you were also called and have confessed the good confession in the presence of many witnesses. (1Ti 6:11-12 NKJ)
Why would Paul tell Timothy to lay hold of eternal life if he already had it?
NKJ Titus 1:1 Paul, a bondservant of God and an apostle of Jesus Christ, according to the faith of God's elect and the acknowledgment of the truth which accords with godliness,
2 in hope of eternal life
which God, who cannot lie, promised before time began,
3 but has in due time manifested His word through preaching, which was committed to me according to the commandment of God our Savior; (Tit 1:1-3 NKJ)
Why would Paul be in hope of eternal life if he already had it?
4 But when the kindness and the love of God our Savior toward man appeared,
5 not by works of righteousness which we have done, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit,
6 whom He poured out on us abundantly through Jesus Christ our Savior,
7 that having been justified by His grace we should become heirs according to the hope of eternal life.
(Tit 3:4-7 NKJ)
Heirs of eternal life? An heir hasn't received his inheritance yet.
And here is John also pointing to eternal life in the future,
20 But you, beloved, building yourselves up on your most holy faith, praying in the Holy Spirit,
21 keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life.
(Jud 1:20-21 NKJ)
Jesus' statement is probably clearest when He says that eternal life is in the age to come.