The Supreme Court has a case before it now asking the Court to decide if discretionary life sentences for juveniles are constitutional. The Court has held previously that mandatory life sentences for juveniles are unconstitutional.
The SC Supreme Court recently upheld a murder conviction for a juvenile who received the mandatory minimum sentence (at least 30 years). The court held, along with which many states have also held, that the Supreme Court will need to decide if mandatory minimums for juveniles is constitutional.
The case currently before the Supreme Court is the DC Sniper case. You can find a paper I wrote about it here.
I believe the Supreme Court will have to resolve Malvo v. Mathena before it can resolve mandatory minimums.