Hello! I quickly flipped through my copy of Carlo D'Este's Patton: A Genius For War (probably the most detailed biography of Patton in existence) and found nothing about plans for a hypothetical offensive against the Soviet Union. However, the general did tell Undersecretary of War Robert Patterson that the United States needed to "present a picture of force and strength to [the Russians]," and if they failed to withdraw to prescribed borders by a certain date, his armies would "push them back across it."

As a bit of trivia, shortly after V-E Day, Patton apparently chased a Soviet brigadier general out of the Third Army's headquarters in Bavaria. The Soviet general wanted Patton to turn over some surrendered Germans. Then, according to D'Este: "Patton calmly reached into a drawer and pulled out a pistol, slamming it on his desk. Then he stood and with sudden rage shouted [to his officers]: 'Gay, goddamnit! Get this son-of-a-bitch out of here! Who in the hell let him in? Don't let any more Russian bastards into this headquarters. Harkins! Alert the 4th and 11th Armored and 65th Division for an attack to the east.' The Russian was shaking and had turned white as he was escorted from Patton's office. After carrying out their commander's orders, Gay and Harkins returned to find a smiling Patton calmly smoking his cigar. 'How was that?' he asked. 'Sometimes you have to put on an act, and I'm not going to let any Russian marshal, general or private, tell me what I have to do. Harkins, call off the alert of the divisions. That's the last we'll hear from those bastards.' And it was."

I'm guessing that's the closest Patton ever came to conflict with the Soviets. :P