Certainly not. Thoracic aortic aneurysms are slow growing, roughly a couple millimeters per year, provided that you are compliant with your medical therapy and lifestyle changes as well as your scheduled appointmens.
In those with an aneurysm less than 5 cm the risk of rupture in the next year is much less than 1%. This risk is considered very small to justify any surgical risk. Elective repair should be considered when the aneurysm exceeds 5.5 cm and definitely beyond 6 cm.