It kinda already does this, but it's so insignificant you can hardly see it. As it recognizes the keyword, it'll change the favicon in the URL bar. I've just tested with "dictionary.com" using my "di" keyword and Google favicon changed to Dictionary.com favicon the moment I pressed SPACE key to continue with the search string.
Chrome has this tiny bit better and it will show a new button like element in the URL bar with full search engine text in it like for example "Dictionary.com" the moment it recognizes the keyword. Firefox doesn't seem to do anything at all though which is even worse. But has more flexible keywording which can also be stored between regular bookmarks, renamed, manipulated by hand and even synced across browsers.
My biggest grudge is inability to use "Y" keyword for Youtube searching or "D" keyword for dictionary.com as they are hardcoded for Yahoo and DuckDuckGo. Which is just dumb as hell.