Sigma is going in with a flu that will get progressively worse as the Arena continues, likely resulting in his eventual death (senior + life sentence in a sterile environment = recipe for disaster). He won't be running for the Cornucopia knowing he'll be a sitting duck, so he'll run away from it and find a water source, damning him to go without food when the sponsors run out. Oops! He won't be killing himself or allow for mercy killing because he wants to set an example, to show other Tributes that there is always hope.

If there's a kind soul willing to help out a dying old man at least once, they would gain Sigma's allegiance and support in the next Arena. Or, here's an easy target, let's see how well he can put up a fight while delirious. :3