Also, when you do a Google search, the product name is now always "Search", even when you started a search in Google News / Images / Videos / Shopping / Books / Places / Blogs / Discussions / Applications / Recipes or Patentes.
With Kennedy, Google has actually reached its goal of becoming a 'universal search engine' and it can finally show a single interface for (almost) all types of queries (except for Maps, Flights and search for personal/private items like email and documents).
You can still access the specific homepages of Google Images and Google News, but Google is slowly convincing users to initiate all their searches from google.com, without thinking about which engine to use. Thus, every search from news.google.com redirects to classic google.com, with the "news" filter activated.
For personal searches (eg Gmail, Reader, Docs, Voice), Google hasn't completely switched to the "filtered results interface". Most of those apps need their own homepage with a list of items (messages, contacts, documents, voice messages, top stories, feed items). However: - most of them have switched to the plain Google logo with the red-colored product title. You can stay in the app or refresh the item list by clicking on the product title instead of the Google logo, which would lead you to the unexpected Google homepage; - most of those homepage (or "item lists") could be merged with Google+ and the new notification bar on google.com, so you could access all your personal things from a classic search. For social results, it's working pretty well since Google Plus Your World: all social items are shown on-top of other results in a classic search. Soon, every new email, documents update or voice message could appear in the notification bar and search results (just like social items): no need to go to mail.google.com, docs.google.com or voice.google.com.
Now (to answer your question), what result do you expect from a click on the Google logo in Gmail? - To go to you inbox? No, that should be the result of a click on the product title, Gmail. - to go to the Google homepage? No, you're not familiar enough with Kennedy navigation.
So my guess is that Google is trying everything to get you to click on products' title to go to/refresh its homepage. Meanwhile, they prevent you from clicking on the Google logo because you wouldn't understand (yet) why you would be redirected to google.com from Gmail.
If this (presumed) strategy work, you would always go to google.com to interact with any kind of products/items, without having to "navigate". Just search Google or browse your notification stream, whatever the type of content (message, documents, web pages...) and its context (personal, social, public...).