They needn't have worried.
Here's the preamble of Hitler's order for Sealion's planning, from 16 July, 1940, which was followed by his radio speech a week later requesting Britain to come to its senses and finish the war:
"As England, despite her hopeless military situation, still shows no sign of willingness to come to terms, I have decided to prepare, and if need be, to carry out, a landing operation against her. The aim of this operation is to eliminate the English motherland as a base from which war against Germany can be continued and, if necessary, to occupy completely."
Note the uncertain language of 'if need be', 'if necessary', etc.
During July, on Hitler's orders the OKW and the OKH independently started planning for Barbarossa.
Goering reported Hitler had told him privately that he didn't intend to carry out Sealion.
The lead Bf 109 pilot Adolf Galland didn't think the project was for real.
Von Rundstedt, who as C-in-c Army Group A was on paper the commander of the invasion force, didn't even bother to attend the amphibious landing exercises.
The navy was naturally terrified about the whole thing, and Raeder told the Army that the navy would only be ready after September 26th, and the necessary combination of tides, moon and weather would mean if the window was missed the invasion would have to be postponed to May 1941.
September 15th is remembered as a BoB climax, but actually Hitler had already told his commanders he had cold feet about the project the day before, and a formal order stopping further preparations went out on September 17.