Given that both of these conditions are caused by poor eating habits or abuse of alcohol, there's actually a lot you can do to minimize the harm. Changing your diet, exercising regularly, etc. can reduce these problems and in the case of high blood pressure get rid of it completely if you're fortunate. If you choose instead to go the medicine route with doctors exclusively, if the meds work you should still expect to live a long life but again, only if you change the way you're living. If you keep doing whatever you did to cause these problems, yeah, it's a death sentence, but even then, who knows when? You could live another 40 years before that happens. Nobody, no doctor, can tell you when you are going to die. They can only tell you that if you keep doing things that got you in trouble you will stay in trouble and it will get worse. The true death sentence is being born. We will all die. When nobody knows.
These things go hand in hand. I have familial hypertension in my family and am prone to it. You control that in similar ways as controlling Diabetes type 2. Diet. Exercise. But if diet and exercise don't control it which is often the case, then there are therapeutic options. There are medications for both of these things that work well! If you are diagnosed with both, you would want to make lifestyle changes of eating a diabetes and hyper tension diet and losing weight if you need to (Try the DASH diet, for example) and possibly see a nutritionist to get the right food selection. And you'd want to exercise if your doctor has cleared you to do so. But then if you treat with the appropriate medications, these conditions become 'controlled' and not doing your body harm. So NO, not a death sentence as long as you treat them with available therapeutic options.
treating high blood pressure: https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/diagnosis-treatment/drc-20373417
treating diabetes type 2: https://www.webmd.com/diabetes/type-2-diabetes-treatments