It seems to be right that the Quran replaced the previously revealed scriptures but still this subject is open for question because it does not completely explain the message of the verse 2:106.
In my opinion one important point is that, if there was any abrogation in Quran or any Scriptures it was stopped with the demise of Prophet Muhammad SAW. However this verse seems to be pointing to a continuing process of abrogation and/or “cause to be forgotten”. That means this verse is not discussing just the Scriptures.
Which are those ‘Ayaat’ that can continuously abrogated or forgotten and replaced with better?
As far as I understand this verse is discussing a phenomenon of changes that mankind is experiencing in every aspect of life since its existence. The continuously changing nature of this Universe.
The root cause of limiting it to Quran or revealed scripture is probably in the understanding of meaning of the word “Ayatin”. This word is considered as to mean only the verses of the Quran or revealed Scripture, although this world is used in various situation throughout the Quran giving variety of definition. By considering all the meaning related to this word one can conclude that Allah SWT pointing us to the phenomenon of evolution in our life.
To understand my point of view first we have to see the different definition of the word ‘Ayat’ in Quran.
We can find this word throughout the Quran however I took some examples that provides some definitions of this word relevant to my opinion,
2:164 Lo! in the creation of the heavens and the earth, and the difference of night and day, and the ships which run upon the sea with that which is of use to men, and the water which Allah sendeth down from the sky, thereby reviving the earth after its death, and dispersing all kinds of beasts therein, and (in) the ordinance of the winds, and the clouds obedient between heaven and earth: are signs (of Allah's sovereignty) for people who have sense.
3:190 Lo! In the creation of the heavens and the earth and (in) the difference of night and day are tokens (of His sovereignty) for men of understanding,
وَ030.020:And of His signs is this: He created you of dust, and behold you human beings, ranging widely!
030.021: And of His signs is this: He created for you helpmeets from yourselves that ye might find rest in them, and He ordained between you love and mercy. Lo! herein indeed are portents for folk who reflect.
و030.022: And of His signs is the creation of the heavens and the earth, and the difference of your languages and colors. Lo! herein indeed are portents for men of knowledge.
030.023: And of His signs is your slumber by night and by day, and your seeking of His bounty. Lo! herein indeed are portents for folk who heed.
030.024: And of His signs is this: He showeth you the lightning for a fear and for a hope, and sendeth down water from the sky, and thereby quickeneth the earth after her death. Lo! herein indeed are portents for folk who understand.
030. 025: And of His signs is this: The heavens and the earth stand fast by His command, and afterward, when He calleth you, lo! from the earth ye will emerge.
030.046: And of His signs is this: He sendeth herald winds to make you taste His mercy, and that the ships may sail at His command, and that ye may seek his favour, and that haply ye may be thankful.
By studying the above verses and many other verses, it is clear that the word ‘Ayat’ is not used just for the revealed scriptures but it is more than that. It can be anything that is a sign of Allah’s Sovereignty.
The dinosaurs used to exist but now they are extinct. People used to communicate using pigeons but no more, even the skill of using the pigeon is rare which once was common. Today we are using emails and cellular phones for communication. Sometime ago people were used to of travelling on the backs of animals now they are not but they are using cars, trains and airplanes etc. There were so many strong nations and dynasties but now we only know their history or many of them probably not even in the recorded history. There were numerous new nations emerged and are still emerging. And the list of abrogation and replacement with better can continue without any end.
These are all Allah’s signs ءَايَةٍ and the process of their ‘abrogation’ and ‘cause to be forgotten’, is continuing. These signs got replaced without interruption in the normal way of life. Even if we look back in our past life, the scene around us is totally changed or transformed. In our life time our loved ones die or depart to some other places and new people take their places. The love of new comers help forgetting those who are passed away. The new cities and towns emerging and so on. We can write books about things which are changed or vanished in our life time.
So what is the conclusion?
I also believe that this is a big misconception that some or any part of Quran is abrogated or forgotten.