As I explained in my earlier post SEO is a process of helping search engines to identify our product or service. Without SEO search engines will not able to identify our website.
Suppose you have a new coffee shop.
Do you have a billboard at the front of the shop?
Did you tell other people about your shop?
Did you publish news paper articles and other publishing methods to introduce your shop?
If answer to all questions is “No”, how could other people knows about your business?
Advertising is a necessity for every business. Likewise every website has to advertise their presence to Search Engines. It is not unethical. In my previous example if the shop owner goes to a customer and threatens him to visit his shop, it is unethical. Likewise if we use bad methods to mislead the search engines and get better rank, it is unethical.
Search engine need ethical methods to understand websites. So SEO will survive for another 5 years and higher.
Check below comments of Matt Cutts.
