The Republicans and Democrats are two cheeks of the same ass. Just as well, I doubt our politics in the future are going to be driven by ideology so much as they're going to be going to be driven by events.
The bottom line is, were broke. At some point in the not too distant future our creditors are going to be refusing to loan us any more money, and what happens then? Where does the money come from to finance all our public services, welfare programs and our big, shiny military? And how are people who rely on those things going to react when the plug gets pulled?
You already have squabbling factions divided up by ideological interests, ethnic interests, economic interests, cultural interests etc. When the going gets tough, tempers are going to be flaring up. And these are things that both parties have been loath to address. Our largest problems are taboo to discuss - how do you solve problems you can't even talk about? At some point, you run out of options.
As for the Libertarians, they are an utter waste of time. Libertarianism demands a confluence of circumstances that plain never conflate in the wild. You don't get to economic liberty by opening your borders to populations with a habit of voting themselves public services. You don't get less government by attacking the relationships that people have relied upon as an alternative to government. You don't get liberty by undermining the institutions that have secured us any liberty at all. Realistically, civilization has been a story of people giving up their individual liberties in the interests of maintaining civil society, not by asserting their individuality to the point of making civil society impossible.