Although new users will get the new uni-bar design by default, existing Firefox users who will update their browser will not lose the traditional search bar.
https://www.notebookcheck.net/Firefox-57-to-drop-the-search-bar.247574.0.html
QuoteRight now, this element of the program's interface is redundant, as the user can search using the address bar.
I don't agree, and I'm sad to see the search bar go. The search bar makes it easier to use different search engines, and if your query contains a dot and no spaces, the URL bar will interpret the query as a domain name instead of a search query, and drop you to an annoying and ugly error page.
with google chrome, if you want to search on some website like youtube, twitter, facebook or google you just have in the adress bar to type "twitter" then hit the "tab" key and it will switch to "search in twitter" instead of trying to search using google/loading a website
I hope mozilla will do the same