What are my chances of getting pneumonia or bronchitis from a seasonal flu?

Depends...: ...On age, smoking or not, asthma or not, and other factors - but, in general, chances of complications go way down if you get a flu shot. And stop smoking if you smoke. And take proper meds for asthma if needed.

Pretty high: If you are not vaccinated depending on the strain of flu etc it can be pretty common and dangerous as the flu causes about 36, 000 deaths /year.

Risk factor...: Seasonal flu is a risk factor for getting bronchitis and pneumonia. Luckily, it is a relatively uncommon complication. Most people with seasonal flu do not develop these complications.