I dunno, a pandemic that never gets resolved and rolls through the summer and fall would be a good excuse to delay an election, too
He doesn't even need to delay the election. In fact, as long as the "economy" isn't completely destroyed, the longer this epidemic lasts, the better it is for his reelection chances in November.
Right now, he's a crisis leader. People are terrified of change on the best days. During a crisis, people look for stability in leadership. If Bloomberg would've been willing to delay taking office, Rudy Giuliani, the specific reason NY voted in term limits, would've remained in the office of NYC Mayor past inauguration day because we were in a post-911 world.
