Well, that link is from 2012. I'm not sure there is any relevance to it today. It would also be worthy to look at what was happening in the news to make Nightline a ratings leader back then. 2012 was a Presidential Election year, with Mitt Romney eventually nominated to take on incumbent Obama. There was Hurricane Sandy that hit the NE, but other than those two events, not a lot of news.
It should also be noted that three comedy network talk shows at 11:30/10:30 are not the norm historically. Yes, we all remember Leno vs. Letterman, but over the past 60 years, there rarely has been a 3-way competition that was remotely close.
Whether all three of the late night shows can survive today is anyone's guess. I don't have a favorite at this point, unlike my younger years where I knew who I liked pure and simple. That may be part of the problem today.
But to your question, no that is not really an option IMO. First, Kimmel would probably not look kindly to being demoted, and would likely get a big contract exit deal that would hurt ABC, (not knowing specifics on his contract). On the plus side, as we approach another Presidential Election in just a year or so (yes, the campaigning will begin that soon!) Nightline perhaps could be a ratings winner once again. Lots of unknowns here, but a good question posed.