Could Rio 2016 be at risk? What would happen if Brazil is not apt to host the Games?

I know this might be a long shot, but I've been worried about the Rio Olympics lately. I know everything seem to come together at the right time but Brazil is really in the biggest political/economic/corruption-related unrest it has been in the past 30 years. I've never seen anything like it and expert says they have never seen anything like it in the past 50 years. The situation is just getting very scary considering it seems possible that it could get worst in the coming months. I think on the 13th we will have clues to what will happen as there will be a big protest rally this Sunday. The population is expected to be on the streets protesting and this time, tensions are at an all time high.

It's sad but I don't think Rio could come in a worst time. People REALLY don't care about sports right now and there is a 50/50 chance that the President will be impeached before the Olympics. This Sunday will be the first of many protests to come requesting the change in Power. Things could escalate and become violent.

I'm very sad and concerned about this. Like I said, everything may end up perfectly fine but would another city (London maybe) be able to host the event given there is military intervention/impeachment/violent unrest in Brazil?

Could Rio 2016 be at risk? What would happen if Brazil is not apt to host the Games?