That means–if the current Supreme Court roster remains in place–six of the nine justices serving when the next presidential term expires will be at least 70 years old.
The three justices who would not yet have reached age 70 by the time the next presidential term ends are Justice Sonia Sotomayor (who was born in 1954 and will be 66 on that day), Chief Justice John Roberts (who was born in 1955 and will be 65 on that day), and Justice Elena Kagan (who was born in 1960 and will be 60 on that day).