Stalin wasn't going to invade Germany before 1942 or 1943. The reason Hitler invaded when he did was to prevent economic collapse; the Nazi economic model was based entirely on territorial expansion by conquest.
Plus Stalin had already learned (or should have learned) that you definitely didn't want to fight a war in the winter. The idea that Stalin planned to launch an invasion in July 1941 is somewhat ludicrous after what happened in the Winter War. The Soviet Army had not yet had time to digest the lessons it had learned, and it had not had time to requip with the tanks and planes it wanted to have on hand. At most, the Soviets might have tried to backstab Germany in 1941 if Hitler had attempted a cross-Channel invasion and gotten his Army and Air Force severely mauled.
Still, whether it was an invasion in 1941, '42, or even '43, if Stalin was thinking of invading, hen invading first was sound decision, even if the execution left a lot to be desired.
