Is COPD life threatening?

Can be... COPD is a slowly progressive disease and, over many years, the damage in the lungs increases and eventually can be life-threatening. The progression can be slowed further via smoking cessation and supplemental oxygen, if your oxygen level is low enough to qualify.
Yes. It can be. If not treated, COPD can be progressive and result in continued loss of breathing capacity, eventually causing death.
Yes. Imagine drowning slowly over 20 years. That's what COPD is like. If you have copd, and continue to smoke heavily, you very slowly deprive your body of the ability to oxygenate your body and mind. Eventually you might need supplemental oxygen just to get from your bed to your kitchen. And having COPD makes you more susceptible to life threatening infections like pneumonia.