I think that is a foregone conclusion and I'm pretty happy about it. KLP is really bringing together the core of Android to have a sleek and consistent look. Card-based themes and slidable side-drawers for everyone!!!
At this point, what apps would even need a major overhaul? The gallery is in huge need of an update. Contacts/dialer, too. I can't think of much else major off the top of my head (I'm sure I'm missing something though).
I'm not even sure what I really want for KLP anymore... Let's get these legacy apps updated to the modern card theme, get SMS support in Hangouts so I can begin to put Google Voice to rest, and maybe unleash a ton of awesome new Google Now cards (anybody else notice they haven't made any substantial update in a while?). Other than that, I'm low on ideas.