Surely after Tarkin & Vader tracked the Millennium Falcon & discovered the Rebels were on Yavin 4 they would've shared that information with the rest of the Empire. You'd think a fleet of ships would've been en route to Yavin to meet the Death Star there & find & destroy any other Rebel ships in the vicinity. If not then, at the very least there should've been Imperial ships sent immediately when the Death Star was destroyed.
My question: how did the Rebels have the time to remain at their base, chill out for a while & have a ceremony? They'd even had enough time to repair R2 to new condition. At the ceremony they were all smiles & laughs! Instead of celebrating why weren't they concerned about a fleet of Star Destroyers appearing in orbit at any second?