The long and short of it is that Congress passes Constitutional Amendments, the Supreme Court makes rulings around those Amendments. Any previous Supreme Court ruling made before the Constitutional Amendment coming into effect would be superseded by the new Constitutional Amendment.

If a Constitutional Amendment addressing abortion were to take place (not happening in the next 20 years, would be way too toxic for any politician to seriously bring up to Congress, let alone get to a vote), then that would supersede any previous ruling by the Supreme Court. From there the Court would make rulings based on their interpretation of that Constitutional Amendment.

To further illustrate the point, we'll go back to the Era of Jim Crow laws. Now, the 13th Amendment clearly abolished slavery, yet the segregation of the races was not mentioned. To speed up our time frame, Plessy v. Ferguson (You may remember hearing about this Court case in school) was the Supreme Court directly stating "Separate but Equal" is valid under Constitutional Law. This is what started the era of Jim Crow Laws, and they would perpetuate for roughly 60 years, until Brown v Board of Education. In both cases, the Supreme Court was ruling over the same Constitutional Amendments (13th and 14th Amendments), but reached opposing results. I bring this up to show that the Supreme Court will rule inside of what is established law in the country, even if the ruling seems to strengthen or degrade the law in question.

In the case of an Abortion Amendment, if it were to clearly state that "Abortion is legal and no moves can be made to weaken the access to abortion clinics," then we would see a move from Conservative states that would further push to define that law. If the State used Eminent Domain laws to buy the land rights where an abortion facility is to sell to another group, would they be directly violating the Amendment by using another Amendment right? That would be a case for the Courts to decide, but they cannot overrule a Constitutional Amendment.