Thank you Joe Dyer for interesting views on cards being banned in the vintage format.
Another aspect that cards will eventually be banned in vintage is a combination of time and the willingness to keep the game of Magic interesting. The goal of Wizards of the Coast is to keep the game going and to sell cards, these two objectives go hand in hand because selling cards generates profits to keep the game going. To keep the game interesting, new and often powerful cards are often printed every year. Lets take into consideration of what happened in 2017. Monastery Mentor made up a large percentage of the decks being played in Vintage, was then restricted and then the number of Monastery decks went down but Monastery Mentor is still one of the primary win conditions in Paradoxical Outcome decks even though being restricted. People play Time Vault and one copy of Manifold Key in their decks as win conditions as do people play Tinker and one copy of Blightsteel Colossus as win conditions; restricting Manifold Key and Blightsteel Colossus would have no effect. Now take into consideration Demonic Consultation and the new Thassa's Oracle, both win the game in combination with each other with Demonic Consultation already being restricted and only needing one Thassa's Oracle to win the game with; restricting Thassa's Oracle would do pretty much nothing. All three examples are a different way of winning the game and require different hate strategies to counter. It appears to me that Vintage in going to be dominated by one type of deck in the future where restrictions will do nothing. All you need is two of a variety of different combinations of cards to win the game. With the availability of tutors, draw spells, Serum Powder and the mulligan getting one of these three card combos into your hand is very likely along with ways to protect them, have disruption and being able to combo within the first couple of turns; and in such a deck a single Monastery Mentor will also work well. I am not sure if such a deck exists today and I also think that I am missing some combinations of cards that work well with both of them being restricted. I am however certain that as the game of Magic progresses there will be more synergies and combos made and that such a deck will dominate the format; where restricting cards will do no good and Wizards will be forced to ban cards to balance the format.