Ok, I will let to be a Japanese fanboy for a momment.
What was constated in Khalkhin Gol, was that the Ki-27 was structurally weaker than the I-16 from the Type 10 onwards. The Soviets fielded a good number of those more modern I-16s in the conflict. Only at the start there were Type 5 and 6 models which were inferior to the Ki-27. They were flown by poorly trained pilots, against which the Japanese reckoned many kills. Later the Soviet pilotos, specially the experienced ones from the Spanish Civil War, constated that this weakness in the structure of the Nate could be explored simply by using energy tactics. As soon as the Soviets started to use this kind of tactic in group, together with the armor protection those I-16s had (it was effectivs against the two .30 cal from the Ki-27), the situation started to become difficult for IJAAF fighters, and pilot losses started to increase, and it was becoming difficult to substitute pilots. Even relatively inexperience Soviet pilots could gain experience more easily against the Japanese planes due to the forgiviness of the structure of the Ki-27 (in the Eastern Front, the 109 or 190 would catch them in the dive easily, and they also could outdive them).
In this scenario, like Tomo Pauk said, the Japanese did not changed much in terms of aircraft. They had a small number of Zeroes, while the Soviets had a similar number of modern fighters based in the Far East by 1941. For the the VVS, that was aware of the Ki-27 weakness, and already have gained experience against the A5M (they also had acess and test flown both fighters), would probably test the structural strenght of the Zero in combat to see if the Japanese learned the lesson, and soon they would find that they didn't learned. With the Oscar the situation would be similar. A surprise would occur with the Ki-44 however.
As for the ground war, yes. Japanese artillery proved outclassed in Khalkhin Gol, and while the Japanese destroyed a good number of Soviets tanks by molotov cocktails (they didn't have much AT guns), the irony was that the Soviets had tanks to lost, the opposite of the Japanese who the majority of their tanks in Khalkhin Gol and already during to the conflict had to remove their tank contingent in order to not have it totally destroyed). The guns of the Soviet tanks, specially the 45mm of the BT's, were much better than the ones of the Japanese tanks. I remember of a passage from Alvin Coox's excellent book Nomonhan: Japan Against Russia, 1939, where a Japanese officers says that compared to the Soviets, the guns of the Japanese tanks were like a penis of a boy.
The Japanese logistics was also poor.
In overall, the Japanese learned many lessons from Khalkhin Gol, but surprisingly, they didn't implemented most of them.
Frankly, I also think the Japanese offensive would grind to a halt, and despite what some Army officers belived, the decision to not attack the Soviet Union was a correct and logical one. The Japanese already commited themselfs to expand to the Pacific, and this occured before KG. The Americans were also becoming increasingly hostile to Japan, and an embargo of oil was a realistical possibility. If the Japanese attacked the USSR, it would be very possible that the Americans would cut their oil. If the Americans cut their oil, and the Japanese get boged down in Russia, Japan would be finished. Vladivostok was only 800 km from Tokyo, and targets in Honshu were all avaliable to Soviets and American bombers, which would could have operated from the Soviet soil. This would brings desastrous consequences to the Empire.
Now backing to the Japanese aviation: the Japanese, despite everything, were learning, perhaps also by watching the aircraft development in other countries, specially Germany (they received a Bf 109 and a Fw 190 for evaluation purposes). The Ki-61 already departed from the traditional sense, as well as the Ki-44, and the Ki-84 and the A7M also. Bombers like the Ki-67 were already in the right direction as well. Actually, late in the war the Japanese were proving to be able to produce planes which at least in theory were very good, like the Ki-84 and the G8N. The problem for Japan was a too much conservative military. In aviation, it can be easily constated that the Japanese planes were not so bad, they were just almost always one geration behind.