I'd guess there's around 50/50 odds either Alito or Thomas die in office by 2032, assuming democrats win the next 3 presidential elections to block them out of retiring. And democrats would need the senate to avoid another Garland situation.
Certainly not impossible that it's only lost for a decade, but I don't love the odds, and am not very comforted by 10 years of strong conservative control.
Ever since Nixon annihilated the Warren Court 45 years ago, there's only really been 3 opportunities to drastically change the court's ideology.
- Thurgood Marshal who resigned for health reasons in 1991 and was replaced by Thomas. Thurgood Marshal didn't die until after Clinton took office.
- William Rehnquist, who announced a cancer diagnosis 2 weeks before the 2004 election, and died the next year. The seat would have likely turned liberal if Kerry had won, or at least more moderate than Roberts.
- Antonin Scalia, who you all know the story of.
So I wouldn't bank too much on back and forth swings here, given how rare the opportunities are, and how hard it is to execute on it. Democrats really need to keep all of Kennedy/Breyer/Ginsburg to hold until they win back the presidency.
Nixon, Reagan and Bush did some serious court packing between 69-93. Carter never got an appointment. Every President usually gets an appointment or 2 aside from the unusual Cater situation.