Arnold Kling posted recently his odds on the economic futures of the United States. I'd rewrite them as follows:

1. 50%. Taxes up, Spending down.
2. 20%. Wealth tax.
3. 10%. Cheep tech for pausing aging and parts replacement. No more social security, everyone works.
4. 10%. Devalue the currency.
5. 10%. Replace social security / medicare with gov't directed individual investment accounts and open immigration doors to the world.
6. <5%. Default.

Numbers may not sum to 100% due to rounding errors. ;)

I put the biggest odds on something similary to the status quo; each party nickel-and-dimes the other to get to a better budgetary setup each year. The AARP may veto that and we end up with some kind of wealth tax negotiated. Everything else is a long shot. Or a really long shot in the case of default.