It's not a coincidence that just as we learn the kind of man Kaido once was, he begins to truly enjoy his fight with Luffy. Something definitely happened for Kaido to adopt his more cynical views, and Luffy putting up a challenge is helping to alleviate that. He may become less suicidal, and thus more dangerous over the course of the battle. Luffy, however, Oda told us during Jump Festa to keep an eye on him, and Kaido once commented on him smiling more when things became more dire.
It could mean Luffy is closer to death in this fight than he ever has before. This will be an uphill battle for sure. I thought Luffy would be mostly alright by the end of this arc, heavily injured, but alright. But now I wouldn't be surprised if his life is in jeopardy just like Zoro once the Mink drug wears off.