Very good research; not sure what any of this has to do with the July 20th plot, but I'm impressed, anyway.
Thank you both.
I needed to think a bit, but I think you can find a connection.
One is connected to the unconditional surrender and the known conditions that would follow. It has been argued that unconditional surrender discouraged some of German generals from making a coup who might otherwise joined a rebellion, since:
"those Germans — and particularly those German generals — who might have been ready to throw Hitler over, and were able to do so, were discouraged from making the attempt by their inability to extract from the Allies any sort of assurance that such action would improve the treatment meted out to their country."
http://www.jstor.org/stable/2614534
Unfortunately you can only get the first half of the sentence above free from the JSTOR link.
The treatment that was about to be meted out to Germany was partly known and partly hyped, and many therefore probably felt it was better to fight on in the hope of securing better terms. Remember what happened in the end after the surrender. You had 25% of the original country annexed by the Allies (most of the annexed areas had been German since the middle ages), 12 million Germans expelled (today its called ethnic cleansing), millions of German military personnel doing forced labor for several years, the country divided etc. That is fairly well known.
Less known are things such as that U.S. troops were forbidden to provide food to German civilians, excess food was to be destroyed or rendered inedible, etc.
http://www.independent.org/publications/tir/article.asp?a=599
You had signs with "You are guilty!" put up everywhere.
http://en.wikipedia.org/wiki/File:Eure_Schuld.jpg
But all that is what happened after the surrender and would only partly be known before the surrender. Before the surrender the German people knew that the surrender would be unconditional, and that the Morgenthau plan had been proposed, thanks to a press leak.
On 11th December 1944, OSS operative William Donovan sent U.S. President Roosevelt a telegraph message from Bern. The message was a translation of a recent article in the Neue Zürcher Zeitung:
(Click on "View Next Page" a few times to get to the text itself)
http://docs.fdrlibrary.marist.edu/psf/box32/t298m01.html
"It took a catastrophe last Summer to bring the internal opposition into the open. Could that opposition offer the German people a better peace than the Nazis? We think not.
So far, the Allies have not offered the opposition any serious encouragement. On the contrary, they have again and again welded together the people and the Nazis by statements published, either out of indifference or with a purpose.
To take a recent example, the Morgenthau plan gave Dr. Goebbels the best possible chance. He was able to prove to his countrymen, in black and white, that the enemy planned the enslavement of Germany."
... "The conviction that Germany had nothing to expect from defeat but oppresion and exploitation still prevails, and that accounts for the fact that the Germans continue to fight. It is not a question of a regime, but of the homeland itself, and to save that, every German is bound to obey the call, whether he be Nazi or member of the opposition."
I forgot to add my conclusion: History would have ended the same way as it did in the real world.
There are too many reasons for the Generals to side with the old regime, so I don't see how the plot could succeed. If it did succeed it would find itself in a position to have to continue the war, since no better surrender terms would be given to the new government. According to a discovery program I saw (discovery mainly produces crap as far as history is concerned, but anyway) most of the actual plotters were motivated by reasons of conscience after finding out about the Holocaust. None of them knew the full extent of it though, I think Canaris though just a few hundred thousand had been killed. It would be difficult to find a motivator for enough others to side with them. Also the Allies were apparently not interested in a coup against Hitler.
"...Instructed to respond to requests from Supreme Headquarters, he drafted proposals for psychological warfare approaches to critical situations at the front only to discover that a SHAEF directive banned calls to the Germans to revolt."
http://www.psupress.org/books/titles/0-271-02314-7.html