Why would you thnk that? The speed iof the victory has little impact on the terms. It is the magnitude of the victory.
The Iran Iraqq War lasted neary a decade and ends with status quo ante bellum basically. The same in Korea
Some rather quick wars- the Franco-Prussian for example, result in pretty harsh terms The colonial warstended to be very short and the terms were usually annexation.
If the allies crush Germany the terms are likely to be very harsh even if the war is over in September 1914.
The competing interests of the allies will be the determining factor. Russia is more interested in destroying Austrian power than German. As no one would object, Austria is being dismembered with Russia, Italy, Romania and Serbia taking what they please
As for Germany, there are two options. Its power is either destroyed as in a Versailles like settlement or the y get off rather easily because it is in someone's interest to keep it strong. The French are likely to want to see it crushed, the Russians much less so. A strong Germany could prevent an Anglo-French anti-Russian alliance.
British interests are likely to be ignored in a short war scenario. The Germans aren't likely to care much about their colonies when the French and Russian armies are pouring into Germany The British lack an army to have any influence until 1916
For a start, the Korean War hasn't ended, technically it's still ongoing. The agreement in '53 was an armistice as opposed to a peace treaty. Secondly, the terms at the end of the Franco-Prussian War weren't harsh, they were designed to do what all terms imposed by a victor were designed to do - prevent a reoccurrence. Territory occupied until reparations were paid was yielded as soon as payment was made. The occupation of Alsace-Lorraine was opposed by Bismarck but was designed as a buffer on the west of the Rhine, not a punishment for the sake of it. Thirdly, colonial wars can hardly be used as an example in comparison to "conventional" wars as the colonial wars were wars of conquest - usually against nations far weaker than the attacking power from the start. The whole point of a nation attacking a tribal area or a native ruler was to take his land so taking his land can hardly be expressed as a "harsh peace". Lastly, and most importantly, Versailles
was a harsh peace as it was
designed to be a harsh peace. The First World War was unparalleled in scope and intensity for the Great Powers involved. With the proclamation of things like the September Programme and Unrestricted Submarine Warfare, Germany made it clear she was deadly serious about making a play for World Power. The idea of Versailles was to prevent that ever happening again. It was flawed, obviously, but it was a peace to end the "War to End All War". This was meant to be a serous undertaking to redraw the balance of power (and the map) in Europe. A shorter war would obviously produce a less harsh peace. A-L would go back to France and reparations would probably be the extent. But OTL Germany had shown herself to be a "rogue nation" and the idea was to emasculate her for all time. The suggestion that Britain, a Great Power (and in a short war scenario, far richer) would be ignored is laughable. Great Powers were consulted simply because of the belief that they
could do something about it if unhappy. Anyway, short or not, Britain was still a member of the Entente and therefore would be on the winning side, entitled to her say.