Biden should have no chance but this country seems to like incompetence as they reelected Obama so who knows. I do not think that Obama would force martial law but I do see a good possibility that events could get really bad where martial law might actually be a reasonable option. If they do nothing to stop the debt from rising at the same pace and we get downgraded it is possible that our cost of money rises, possibly substantially then our debt would be out of control Obama care is going to be a huge addition to the debt, as it already has issues and we are in the good part. I could see our financial system unraveling pretty quickly which would lead to big problems pretty quickly. People stop getting their free money and jobs become harder to get there is sure to be some kind of civil unrest.
I absolutely do not see Obama doing anything to dampen the rising debt and sadly I do not think the House has its heart into it either. With no one looking to cut spending our rising debt could really get out of control. As the debt goes up the amount of interest increases if the rate of interest goes up the debt climbs even faster. Not a very good loop. Government reacts by printing more money, inflation is off and running and well everything just goes to crap because there are very few options they have left in the bag.