Is it worth building a website for the long run?

I am thinking about building a very high quality website which I will eventually rely on for full income, to replace my current employment. Is it worth building a site with a view to 15 years ahead? I don't want to dedicate so much time building up a site only to find people moving away from using websites 4/5 years down the line to some other new technology. It will be a big waste of time and effort. We have a family business, in the restaurant trade, situated at a tourist attraction, so it won't be the end of the world if the website fails. But my goal is to eventually rely on the site for full time income because I want to do something intellectually more satisfying than just running and working in the family food place. I have been studying for a degree and gaining some experience working part time in a business related to my degree. However, I want to now create my own site providing analysis of the industry. This is a big niche and the traffic potential huge. The top sites get millions of uniques a month.

I know about the competition, SEO, etc that needs to be considered, but for now I would simply like to know whether websites would be viable 10-15 years down the line.

By the way, this will be a content site, built entirely for the user and not search engines (not to be confused with search engine optimisation), not content developed to sell products. Revenue sources like Adsense, which I will be using to earn revenue, will be an afterthought. I know how important it is these days to build content for the user.