So those of us who are not quite old are used to a historically steady kind of Democratic and Republican party. Obama isn't all that different from LBJ; Bush wasn't all that different from Nixon.
Could this change? Well, maybe. There's a lot of different ways it could go.
The US political system has gone through periodic titanic shifts. The Federalists and Anti-Federalists are obviously no more. Of course the Republicans came about in 1860 looking very different from how they do today--and capturing a very different part of the electorate.
In 1960, Kennedy won the South, Mississippi region, and the Northeast, where Nixon managed to somehow win California, Oregon, Washington... and Idaho, Indiana, and Kentucky. Kennedy got... West Virginia, Texas, Alabama, and... Massachusetts.
But then the Baby Boomers came along, the Republican Southern Strategy emerged, and the map hasn't changed all that much since then.
But times, they are a'changin.
Enter the Young'uns
The Millennials are on their way, and are becoming the biggest voting bloc in the US.
They don't vote nearly as much, yet, but they are voting more often over time.
Right now the Democrats--and nobody--appeals much more to them than the Republicans. They're highly dissatisfied with both parties at the moment, and the Republicans in particular seem to be losing big.
They can't stand Trump (only one in five Millennials want to vote for him, which is a historic trouncing), and Gary Johnson is doing almost as well as Hillary Clinton among them. The more racist and xenophobic appeal of the older generations just isn't getting traction with the young one. I think this is getting to be the last major presidential election where such ideas dominate.
A Change in the Conservative/Liberal Divide
It seems that Millennials don't line up with the conventional attachment of liberalism vs. conservatism in both social and economic issues.
Socially, they're on average pretty liberal--a bit less so than President Obama.
Economically, they're quite moderate, closer to someone like Chris Christie.
More than other generations, they think that government intervention in the economy is a bad idea... but they seem generally agreed that higher taxes on the wealthy and more help for the poor is a good idea. So it may be a Hayek-style economics of free markets with a very strong social safety net. This is actually a lot like Germany and Austria. There will of course be differences in the bell-curve, but each party is going to have to change to grab this group as they become dominant.
What About Wedge Issues?
I'm sure there will be new ones a'coming for the young folks, but the old social conservative vs. social liberal divide might be dying.
For example: this generation is pretty pro gay-marriage. That issue is just dead.
What about abortion? This gets more odd: 75% of millennials are pro-life; 65% are pro-choice. Unlike "they just can't make up their minds, stupid kids," the evidence seems to suggest that they're morally torn about abortion (they think it's a little dodgy), but they still want to to be very widely available. It's a pragmatic bunch that seems to be willing to put aside its moral feelings for a solution that feels very practical and hands-off.
Will there be new ones? Probably--I don't think those are going away. But they're more likely to be Liberal (in the sense of "liberty") vs. Progressive. So the debate over Free Speech vs. Social Justice is a real one, and very divisive, quite emotional--classically wedgey. But it's not about social conservatism. vs. liberalism anymore. In fact, the conventionally "right-wing" type folks seem to be the ones defending "total freedom," and the conventionally "left-wing" type folks are looking for more restrictions in behavior in order to further the greater good.
What Could the World Look Like in 30 Years?
If I had to speculate, I'd say that the realignment in the US will make the parties look more Liberal vs. Progressive than Conservative v. Liberal. The Republicans, in particular, getting totally hammered by Millennials, are going to be looking for a way to grab them. A lot of them like free markets, and many of those happen to live in places like Silicon Valley, Denver, Austin, and the like.
So the map may start looking different, too. Of course there are many other factors going into this--ethnic and racial demographics, immigration, population movement, and the like--but we'll look into those later.