I am a 33 yr fit female with hypertension, white matter changes on mri and vertebral artery stenosis found in mra. could i have a stroke soon?

NO: Those don't predict a stroke. You can occlude a vertebral (100%) and not have a stroke as the brain receives other blood supply that is connected. Be sure your blood pressure is controlled and keep it there!

Perhaps.: You are probably at higher risk than average for having a stroke. I would recommend taking an adult aspirin a day and modify your risk factors (blood pressure control, healthy diet, weight loss, smoking cessation, cholesterol control, etc.). Speak to your physician for more information.