There is no doubt that Adolf Hitler would have ordered the invasion of the Soviet Union, Operation Barbarossa, irrespective of the outcome of the war against Great Britain. War with Britain was not one of Hitler’s overwhelming priorities. Invasion and annexation of Russia, in contrast, was central to his vision of Germany’s future. Hitler was imbued not only with a sense of German racial superiority, but with Germany’s destiny as the ruler of all of Europe.
Hitler’s views on race were intertwined with those of Germany's and Austria’s future, as Hitler believed very fervently that his goal of a purified Germanic race was threatened, in his mind, by two comingled factors: Judaism and Bolshevism. Hitler also believed that Germany and Austria required far more territory than these two nations possessed to accommodate their growths and to provide access to raw materials needed for industry (he envisioned the merging of the two nations, realized, temporarily, with the Anschluss). That the vast Russian plains were occupied by the Slavs and the Bolsheviks, and that the latter controlled through what he perceived as the pernicious influence of World Judaism, provided all the incentive Hitler needed to covet Russian territory. As the German leader remarked in a 1937 speech, there existed “an uncivilized, Jewish-Bolshevist, international league of criminals” based in Russia that threatened the world order and that had to be ruthlessly eliminated.
It is important to note that, while Hitler’s writings and statements throughout the 1930s were replete with examples of his hostile intent toward Russia, he was wary of more-blatantly threatening Russia, as its paranoid and equally ruthless leader, Joseph Stalin, was paying attention to developments in Germany and Hitler recognized the need to play East off against West for the time being. The Nazi-Soviet nonaggression agreement of August 1939, known for the two nations’ foreign ministers, Molotov and Ribbentrop, was a tactical measure on both dictators’ parts, negotiated to buy breathing time.
In conclusion, the invasion of Russia would have been launched irrespective of events in Great Britain. The concept of Lebensraum was synonymous with Hitler’s vision of the future, and the German leader’s intentions in this regard were only briefly, following the signing of the August 1939 agreement with Russia, rendered opaque to observers.
(See, also, page 123 of the translation of Hitler's Mein Kampf linked to below for a quote on the author's view of Russian land and its historic importance to "the new German Empire.")