The Chazon Ish (Y.D. Treifos 5:3) discusses that there are many treifos nowadays that can be healed through surgery or other means and wouldn't die within 12 months. Would this undermine chazal's assumptions and allow us to consider many of their treifos to be kasher? The short answer is: absolutely not. The long answer is: Chazal were put in charge of establishing the treifos in the first 2,000 years of the world, and this would establish the dinim of treifos for all generations. All illnesses and injuries that at the time of chazal were not able to be healed, were considered treifos and forbidden by the Torah for all future generations. He then goes on to say that there may have been physical changes in the anatomy that would explain why the problems of then would not be problems now, and perhaps the modern day surgeries would not have even worked then. With this he explains the Rambam who on one hand legitimizes the claims of doctors to be able to heal many of the 18 treifos listed by chazal, yet holds that they remain assur to eat even today.
The Rambam writes:
רמב"ם פ"י מהל' שחיטה הל' י"ג - וכן אלו שמנו ואמרו שהן טריפה אע"פ שיראה בדרכי הרפואה שבידינו שמקצתן אינן ממיתין ואפשר שתחיה מהן, אין לך אלא מה שמנו חכמים שנאמר "על פי התורה אשר יורוך
Based on this, the Chazon Ish explains that although at the time of the gemara where the 18 treifos would die within 12 months, if a man had one of these ailments and then disappeared we would allow his wife to remarry on the assumption that he died. Nowadays, there would be a distinction between allowing his wife to remarry and eating a treifa - we could not eat the treifa, but recognize that it could be healed and wouldn't allow his wife to remarry.
The gemara in todays daf tells that the uterus was removed from a cow and R. Tarfon paskened that it was a treifa, until he was proven wrong by the Chachamim in Yavneh who sided with the testimony of "Tudos the doctor" that such an animal can live. Based on the Chazon Ish, why is the testimony of Tudos a clear proof that R. Tarfon is wrong? Why can't we assume that the removal of the uterus is a treifa, just that they later figured out a way to remove it without rendering the animal a treifa, similar to the suggestion of the Chazon Ish? This gemara would force us to say that until the seal of the Mishna, any cure that they were able to devise and introduce that would be effective, would be evidence that it was never meant to be included in the list to treifos. The Chazon Ish's principal would only apply to surgeries and remedies that were developed after the close of the mishna.