The spigot is running. In a 5-4 decision, Kagan wrote for the majority striking down a life sentence for two juvenile offenders who received life sentences in homicides. Both were fourteen years old. The Court was ruling in Jackson v. Hobbs and Miller v. Alabama.
Update:
The Miller and Jackson decisions are here. The essential point is that mandatory life sentences – where a jury may not consider mitigators – are unacceptable for children of such tender age. It seems fairly clear – and certainly clear from the dissents – that this rule applies to children up through the age of 17.