I'd love to be wrong, but I don't think so. If anything, I think it would be a pretense to get out of whatever he had planned for tonight or the next week, or just a distraction for something coming soon.
I feel like they wouldn't have made the other announcement that he'd step down if a medical condition arose right before saying he's got covid if that was the case though. My expectation they want to clear the way for a new nominee at the convention that's just a few weeks a way now. We'll see soon I guess.