Spotted on Twitter via @rgomezric, Bing is testing a new search bar and navigation. The new bar and navigation has two main differences:
(1) The Bing logo is no longer accompanied by the Bing name written out. Now it is just the logo.
(2) The "web" navigation filter for the search results was changed to "everything."
The search bar also looks larger and more spacious on this new test.
Here is a picture you can enlarge:
Forum discussion at Twitter.