Gilmore Girls has always been about the Gilmore women. The relationships between three generations of strong, unique women is what holds the show together. But throughout the series, there were men who impacted the lives of Rory, Lorelai, and Emily, and therefore the show. One man who actually affected all three Gilmore women is Christopher Hayden, Lorelai's first love and Rory's father. Christopher will return for the Netflix Gilmore Girls revival, which makes total sense, as he plays an important role in the series. He was always a presence in the original series in some way, even if Rory and Lorelai could never fully count on him to show up. Fittingly enough, it's still not clear which episodes of the Gilmore Girls revival Christopher is in, though it seems he won't be a big part of it.
Even though Lorelai was briefly married to Christopher, she rightly ended up with her soulmate, Luke, in the end. For this reason, I'm not worried that Christopher will shake things up in the revival and actually glad he will return. He's a character that has impacted everyone on Gilmore Girls and it's only right that we see what he's been up to for the past 10 years. How much we'll actually see hasn't been confirmed, but IMDB lists actor David Sutcliffe as only appearing in the final episode, "Fall."
IMDB listings are not always accurate so this could change, but right now, it's the only clue we have. Sutcliffe hasn't said much about his role in the revival, though he did talk to TV Line about Lorelai and Christopher's relationship at the premiere:
To me, this lack of closure confirms that while Christopher is in the revival, he won't end up with Lorelai or as a permanent fixture in any capacity. And I have to agree with Sutcliffe about his character. Onn a show about human connection and love, he has always represented a missed connection. But with the revival, every character gets a chance at redemption. Hopefully, even without closure, we'll get to see that Christopher has grown.