As long as there are websites and search engines there will always be SEO. SEO is the art of putting a website in the best possible position to thrive in the search engines. SEO can be as simple as making an accurate title tag to publishing and marketing an article on your site.
SEO will always exist but the methods will not always be the same. Search engines change therefore SEO practices must change. It is important to be up to date with the most recent SE changes but there will always be a standard set of rules to follow when building any website. Sometimes people in the SEO industry focus on SEO too much and not on the actual quality of the website for its visitors.