Retired Justice Stevens suggests Supreme Court may advance gun rights
First the factual aspect. Assuming it's accurate, it confirms something the gun rights community has long suspected. (I don't particularly doubt the accuracy of the claim, although Stevens may be overstating his own role as as persuasive force...)
Now the facts.
We don't know where the current court sits on gun rights. Roberts has demonstrated squishy behavior before. Kennedy was replaced with Kavanaugh, presumably a solid 2nd Amendment vote, but Trump's first pick Gorsuch replaced Scalia (solid pro-gun vote) with a presumably solid pro-gun vote. Neither Kavanaugh nor Gorsuch have really been tested yet and Roberts is untrustworthy. We're probably better off with Kennedy replaced. But we need to win one more to feel secure, and even then, we can't count on the new Justices until we see how they vote.
Since Stevens is clearly trying to stoke panic here, let me rebut.
Gun free zone laws around schools have stopped precisely zero school shootings. As with other places declared gun free, criminals view them as soft targets. The only people deterred from carrying in such zones are the honest, law-abiding people who you would want to have a gun in case of such an attack.
"Laws intended to keep firearms out of the hands of especially dangerous individuals" has a couple possible meanings. Do they mean felons? Most felons will be able to get a gun as easily as they can get drugs, ie, illegally. Challenges to the core of felon-in-possession laws seem unlikely in the near future, though we will likely see nibbles around the edges for people acting in self-defense, whose crimes were not violent in nature, and who have been rehabilitated into society. Do they mean people like the Parkland shooter, who should have been on the naughty list but was not due to law enforcement failures? Law enforcement will have failures no matter what laws you pass. Do they mean people like the man who died at the hands of police in Maryland recently? How many innocent people need to die because one of their in-laws didn't like them owning a gun?