From what I've heard, Kings Of Leon have begun soundchecking lots of new songs, but I don't think they've made much progress in the studio at this point, so if Al's going to take them on, it looks like it'll be in the form of a parody. This makes me think he's not going to touch them at all though; I think a Kings Of Leon parody would be great, but they have a tendency to not use a whole lot of words in their songs. So unless Al has a really good idea, I can't imagine he'd go after a song that, for all practical purposes, has almost no lyrics.
I definitely agree that it looks like there's a method to Al's madness regarding the list of songs in the new polka medley. However, it saddens me that this is the first medley in which I'm not familiar with all of the included songs (there are three towards the end that have eluded me entirely). I've finally slipped to the other side of the pop culture curve! Oh, the shame!