The Supreme Court can always overturn its previous decisions. It did so just last week, in fact, when it decided that states can charge sales tax on out-of-state purchases. See https://www.npr.org/2018/06/21/606463186/online-purchases-to-cost-more for details.If Roe v Wade and gay marriage are good law, why would anyone worry about them being reversed or set aside or whatever.
For a more famous example, consider Plessy v. Ferguson, and its followup, Brown v. Board of Education.