To be fair, Kendrick has also said that there are darker stories he can tell. I'm not worried about the narrative, even though I know a lot of people will automatically dismiss it as either being too much like GKMC or not enough like GKMC ("it's not as thematically consistent!"). Which goes back to my view that he can't win.
Not worried about the flow either. He has recorded scores of demos and is experimenting...I like that. To often in rap there's very little focus on using a studio properly, and not as a place to make hundreds of throwaway tracks (see: MMG) that drain your creativity.
He's working with some heavy bass producers (Thundercat, Pete Rock, Quik, etc). He'll be weaving in and out of beats, I'm sure.