posted by gutRight, and the lower courts generally need to find a legal challenge or exception to precedent, and then higher courts have to agree. Or multiple cases that have a difference of opinion throughout different district courts.
And I don't know that there has been many cases that actually threaten Roe v. Wade to even come close to the SCOTUS. I hope so, though, because it would finally put an end to "OLD WHITE MEN WANT TO TAKE YOUR ABORTIONS AWAY!!!!"
I've read more and more the end of Roe v. Wade will be death by a 1000 cuts. Roberts does not want to go down as overturning it, rather that to just not hear or uphold more and more restrictions that states pass.
I also don't think Trump goes full anti Roe v. Wade in his nominee as he needs the two women Rs in the Senate who both back Roe v. Wade.
On a sidenote, Kennedy retiring also pretty much kills any challenge to partisan based gerrymandering cases. He was the real driver for the court to hear them. Fivethirtyeight had a good podcast and series on the complexities of those cases. Pretty interesting as both parties use it to maintain control.