The top navbar isn't the only thing Google is trying to get rid of, some users have spotted a version of the Google Search page that comes without a search box.
This seems to be related to the Google Search integration for Chrome that the company has been working on.
In fact, you can test the new search-box-less search results page by enabling a Chrome flag, "Enable Instant extended API."
This feature is still in testing and doesn't work very well all the time, it's only barely usable in the Windows version of Chrome.
If you enable the flag, you'll notice that the Google homepage is added to the Chrome new tab page, logo, search box and all.
This has been the case for a few months now, but more recently Google has taken the experiment further by eliminating the search box from the search results page.
Doing a search from the new tab page or from the Omnibox will lead you to a results page without the search box.
You'll notice though that the Omnibox will not contain the Google Search URL but rather the initial query, essentially, Google is replacing the search box on the page with the Omnibox, something most people had already done in their regular usage.
You can replicate this without enabling the Chrome flag, by adding a few search parameters to any Google query URL namely: "&espv=10&ie=UTF-8".
What's more, modifying the value of the "espv" parameter, using 101 for example, will result in different versions of the search results page, with a slightly different header.
All of this indicates that Google is actively experimenting with this new design, but it's clear that the company is very determined to get this done and get it right.
Given that most people start their searches from the Omnibox, making that part of the search page makes sense, especially since this is Google's browser. The company has said that it will open up the APIs to other search providers though.