Of course it will last to 200k+. Campervans always fetch decent money so even at that mileage it will take something very unlikely like a catastrophic engine failure to give pause and even then probably still worth repairing (even though not using main dealers of course).
The main reason vehicles that are otherwise desirable (like a camper) become un-economic to repair is usually due to bodywork deterioration, not mechanical stuff. The VW vans are galvanised, which helps. But if you really want to give it the best chance, get it up on a lift once a year and have someone poke around with a big ugly screwdriver to find any rust spots early and get them dealt with, by wire brushing and treating with rust killer for surface rust, or judicious welding of anything that's getting bad. On the bodywork, any surface bubbling should be investigated as soon as you see it because it's usually a symptom of water being trapped inside a door, tailgate or whatever. Big stonechips will go rusty but they're very little problem, just whack on some rust killer fluid and a dab of paint.
Although not vans, I own a number of vehicles aged between 40 and 60 years, and two that are in their 80s/90s. Any vehicle can live to old age if you keep on top of things, get to know where to look to head off common problems, and accept that things sometimes break unexpectedly but everything is ultimately repairable.