Demographic trends won't be enough, and assuming that leads to dangerous complacency.
The Democrats have a future if and only if the Justice Democrats -- a sort of left-wing Tea Party movement -- succeed in transforming the party. In economic as distinct from social terms, the Democratic Party in its current form is not liberal enough to win. There is far too much corporate/Wall Street/1% influence. That is one reason why Trump won -- the American people do not want the plutocracy we have now, and many voters somehow concluded only Trump could and would fight it, partly because the Democrats have presented no real opposition to the plutocracy for decades now. But if the Democrats become a real left-populist, social-democratic party, then they can win.
The Democrats have a future if and only if the Justice Democrats -- a sort of left-wing Tea Party movement -- succeed in transforming the party. In economic as distinct from social terms, the Democratic Party in its current form is not liberal enough to win. There is far too much corporate/Wall Street/1% influence. That is one reason why Trump won -- the American people do not want the plutocracy we have now, and many voters somehow concluded only Trump could and would fight it, partly because the Democrats have presented no real opposition to the plutocracy for decades now. But if the Democrats become a real left-populist, social-democratic party, then they can win.