If you suffer from gingivitis and you leave the gingivitis untreated it can progress and become periodontitis which is a much more severe form of gum disease.
When the gum disease progresses the infection can get into the bloodstream which can then possibly lead to death.
If you treat the gingivitis in time and keep your teeth healthy to prevent future gum disease you should be just fine.
It's rare to die of gingivitis but it's highly possible for death to occur if gingivitis gets more serious.