As-Salaam alaikum,
About ayat 51 of Surat Shura quoted above, as I understand it, the verse/ayat states that all men do not have the faculty to talk to Allah, Subhanahu Wa Ta'ala, but some of His Special Servants do have it. Allah talks to them in 3 ways:--
(1) Revelation (Wahyi directly sent to Prophets).
(2) By sending some angel as a Messenger
(3) From behind the veil.
The first way above has ended upon the last Prophet Muhammad, Sallallahu alaihi Wasallam, and the second way also... but the third way is still continued through which Allah converses with His Friends (Awliya)..."from behind the veil". Here, veil means our physical body behind which the soul is always talking to Allah.
Just as an alive body is blessed with 5 senses and other outward powers, similarly an alive soul also has senses and powers; infact its senses and powers are stronger than the physical body but are dormant due to the ignorance of humans towards the reality of their souls. A case to prove this is shown in ayat 172 of Surat A'araf (7:172) where Allah asked our souls...
"Alastu bee Rabbikum... AM I NOT YOU RAB..?"... all souls replied: - "Yes! You are"! meaning that the souls heard the words of Allah,
analyzed them, thought about the answer and replied by speaking. That was a time when physical bodies were not created, and all the senses and powers of the soul were active.
Best Wishes.
I would disagree with somethings you said.
Revelation, wahi to Prophets includes the divine scriptures (Quran, Torah, Gospel & so on) but is not limited to this meaning only. As word Wahi has also been used for non-prophets in Quran & is used as reference to Inspiration. So wahi is both revelation & inspiration.
Inspiration can be in form of mental suggestion, intuition or maybe even dream or vision?
As we are informed in Quran, Prophet Moses's mother was inspired to leave Moses(pbuh) in stream (28:7) which mother has the heart to do this? It was inspiration from God to her. Similarly we are told Prophet Muhammad was informed by Allah about his wife telling his secret to other wife, she asked:
And when the Prophet confided to one of his wives a statement; and when she informed [another] of it and Allah showed it to him, he made known part of it and ignored a part. And when he informed her about it, she said, "Who told you this?" He said, "I was informed by the Knowing, the Aware."
So this wahi-inspiration to the Prophet was not revelation (Quran) as it is not mentioned in Quran, neither does the verse indicate that.
This Wahi-inspiration is open & accessible to all humans acc to 42:51
But it cannot be substituted with Revelation-wahi (Quran & other scriptures)... and hence this cannot be argued as argument for support of hadith. Neither is it supported in Quran as that & Quran informs that there is inspiration from satan as well.
Hence criterion for guidance must be Quran to determine any spiritual experience is from God or something else.
So Wahi in sense of inspiration is not over and is open to ALL humans.
I spoke with Shaykh Ibrahim Gamrad who told me he converted to Islam after having spiritual experience in which he realized oneness of God.
Also the second point, contact through Angels has not ended either. No verse of Quran states that. And no verse states this contact is limited to Prophets only, on contrary 42:51 states that this contact is open to all humans.