When the world replace the US Dollar as reserve currency the USA will definitely get into another depression. A lot of countries will suffer but I believe the USA will have the hardest time of them all.
The world cannot simply accept the USD forever since the Federal Reserve just keeps printing more and more all the time.
There is a reason gold and silver have skyrocked to record levels and there is a reason countries all over the world tries to get rid of all their US treasury bonds.
I would advice all US citizens to save some of their money in gold and silver, remember that you dont lose your money you just replace it in another currency. Gold and silver will never go down to zero unlike the USD that have that possibility.
http://4.bp.blogspot.com/_TKwsCwZoDHg/TKv2HML1YjI/AAAAAAAACKk/gZoHJr-VQcY/s1600/Inflation-1923.jpg