As we know (and as has been extensively discussed on here), Sealion in 1940 is never going to happen for many, many reasons. Most of them revolving around the Heer and Kriegsmarine not being suicidal.
So what if Hitler realises that Sealion is a dead-duck but is unwilling to go to war with the Soviet Union while he still has an active enemy in the west? Can Germany afford to leave the USSR alone until the UK is dealt with (no matter how long that takes)?
If Hitler decided to give the Luftwaffe another go at gaining air superiority while giving the KM time to build a (slightly) more credible invasion fleet, how does the USSR react? Are the theories of the Soviets preparing to go west as the Germans started their advance east true? Was a war between Hitler and Stalin inevitable even if it's not Hitler that initiates it?