There's no predicting this kind of thing. Best you can do is have the car thoroughly checked over, top to bottom. Being a VW you are going to have little things go wrong and that's just the nature of the beast. So if I were you I'd be more concerned with tires, shocks, CV joints, suspension, brakes & rotors and electrical devices than I would be with the engine.
if this car has the 1.8 turbo motor, however, I would definitely recommend synthetic oil and would have your mechanic check the engine for signs of oil sludge.
As a general rule, most modern engines can easily go to 175,000 to 225,000 miles, so figure your car's life is half over, or a bit more than that.
Much of your question depends on the car's previous service record, if you know it.