I think that Hitler would have been satisfied with a ceasefire, leaving the UK intact, but out of the war.
If that happened, then he would be able to turn his attention totally towards the USSR, but that's essentially what he did anyway. The reason he couldn't devote all his troops there was not fear of British invasion, but to secure the nations he conquered (and bail out Italy).
However, if Britain was defeated, then D-day would have been impossible for the simple reason that there wouldn't have been anywhere to land before the invasion. Assuming that the US still gets involved due to Pearl Harbor, then they'd have to invade though Africa. I think that Germany would probably still have been defeated, but it would have been much more difficult for the Allies.
Its hard to say how it would have affected the USSR, but assuming that Hitler still makes the mistake of abandoning his forces at Stalingrad, it would have probably turned out the same.
In the Pacific, the US would have been weakened by Germany, but they still had a better navy, and eventually nukes.