Hitler was said to have committed suicide when Germany was losing the war as the British troop advanced forward to Berlin.
So do you seriously think that the 'mightly' Lord Voldemort would do that? I don't really think so, because it is simply weird to kill of LV like that!
As for relation of the second war with WW2, the Allied consists of many countries like U.S, Great Britain, France, Russia (can't remember all) while the Axis (is it called the Axis???) consists of only Germany, Italy and Japan (not too sure abt Japan).
If a country represents a race (either muggle, elves, centaurs), it make sense, don't they?
On LV's side, we have the Death Eaters, Dementors and probably Giants
While on DD's side, we have only wizards so far. Similar to what happened in WW2, Great Britain was the only country to stand up against Germany in the starting and after sometimes (a year or two), others started joining. So I believe there are much more allies to come along.
And...did Russia first joined the Axis and later the Allied, because Hitler went back against their promise and attacked Russia? If so, maybe one of the allies of the dark side will switch over to the good side.
I could be entirely wrong about this history because this is what I remembered, not memorised