Can pulmonary hypertension get better without treatment?

No. Without treatment, the condition is life-threatening. There are many factors that influence survival such as age, sex, presence of heart failure, etc. Thus, it is best not to make a general statement about prognosis before a thorough evaluation. Some keys to survival are early diagnosis and treatment.
No. Pulmonary hypertension can be idiopathic (unknown cause) or secondary (due to diseases such as blood clots, emphyema or pulmonary fibrosis). Generally speaking these are serious and potentially deadly illnesses that will not get better without specific treatments.
No. Classic pah is a progressive disorder. Any delay in treatment affects survival. Sadly the presenting symptoms are non specific. And require a high index of suspicion when evaluatin a pt with unexplained dyspnea.