You saw the Heller vs DC USSC decision in 2008. That decision was 5-4. By one vote. The whole country almost lost the individual right to keep and bear arms. By one vote, 60million Americans were almost made instant felons.
If Hillary gets elected it wont be too long before it will be 6-3 or more the other direction.
The remarkable thing about the SCOTUS and the 2nd Amendment is how little the Court has said about it over the years. After more than two centuries, Heller is just about the only Supreme Court decision that opines on the meaning of the Amendment's predicate clause, and holds that the RTKBA is an individual right, not a collective one to be exercised by means of membership in a militia. Post-Heller, the focus should therefore be, as with other individual rights, the extent to which reasonable restrictions can be placed on the right. Obviously, reasonable minds differ about that, but at least the starting point is clear - the individual right to self-defense is Constitutionally-protected.
But Hillary wants to overturn Heller, and with Scalia's passing the Court's balance is poised to change. There is far more Constitutional latitude to curb gun use and ownership if Heller is overturned, even if it isn't necessarily replaced with an affirmation of the right as merely a collective one.
While the best solution has always been to make sure Hillary never gains the White House, that hope is now gone. But I think the political climate will support a Constitutional amendment that essentially codifies Heller before a Clinton SCOTUS can do its damage.
I think this needs to the focus of Second Amendment advocates going forward - a simple, one-sentence amendment that codifies Heller before it can be taken away. The Constitutional amendment process - requiring ratification by two thirds of the states - is difficult but favors red-state issues because Wyoming has the same power as New York.
A Clinton Presidency doesn't mean all is lost. Indeed, it could be the event that galvanizes Second Amendment advocates to muster the political will to do what the SCOTUS itself avoided doing for 200 years - make damn clear that the right to self defense is Constitutionally-protected for you, me and everyone else.