promises, blessings... then justification and then... covenant??

I am off to France tomorrow to speak at a small one day conference; my topic is the covenant. I have been re-reading some of the classic passages and was arrested by the passing comment in Hebrews in the account of Abraham's meeting with Melchizedek. It reads...

but he whose genealogy is not derived from them received tithes from Abraham
and blessed him who had the promises. Heb 7:6

I have noted this in the past but it caught my attention again today. Abraham had received promises long before he met Melchizedek. He received a later blessing from Melchizedek to add to the promises. This is all in Genesis 13-14 but he is not 'justified by faith' until Gen 15:6. This is prevenient grace at work; justification came later. Gen 16 then tells the story of the birth of Ishmael and consequently God's personal covenant with Abraham, sealed with circumcision, comes at least 14 years later in Gen 17.

I am not trying to create a doctrine or a necessary pattern but just observing the record that justification can, apparently, take place much later than first hearing God's voice AND much earlier than a personal entering into covenant with God. So what condition was Abraham in during those 'gap' years? I hear the familiar question... "but would he have gone to heaven...?" He was 'right with God' how could he be kept out?

Suppose we transpose this scenario to the New Covenant. Can a man or woman be 'right with God' before they enter into the New Covenant? As the New Covenant is first mentioned in Jeremiah 31 all the 'heroes of faith' recorded in Hebrews 11 were 'right with God' long before the New Covenant. Would this go some way to giving an explanation for so many today who have taken genuine first steps but for whom the 'better things' of the New Covenant are still beyond their reach? Makes you think doesn't it? ... or, at least, it ought to.