You really don't need to look very hard for evidence that The New 52 wasn't planned very far in advance, at least not in the form in which it was actually published.
-Brian Clevinger and Brian Wood being kicked off the Firestorm and Supergirl relaunches, respectively, in favor of reboot pitches, after being told that they had the gig based on plans relying heavily on existing continuity
-Justice League: Generation Lost ending on a cliffhanger unresolved due to the reboot
-Brightest Day ending on multiple cliffhangers (Martian Manhunter, Firestorm, Hawkman) unresolved due to the reboot, while Swamp Thing's, Hawk & Dove's, and Deadman's storylines arbitrarily remaining in continuity
-Gail Simone's last issue of Birds of Prey setting up future storylines, with letter page referring to upcoming issues with her as writer
-Batwoman #1 coming within weeks of shipping in April of last year, with previews advertising that date being published throughout the DC line
-Teen Titans referenced as past team in Batwoman #1 and Teen Titans #1, yet subsequently decreed by editorial in October that there had been no prior team by that name in current continuity
-Scott Lobdell claiming in pre-relaunch interviews that Superboy wasn't a reboot, subsequently calling process for determining what is and isn't still in continuity
"organic" and stating that Superboy had been determined to be a reboot after all
-Martian Manhunter referenced as past member of the Justice League in Stormwatch #1; dialogue explaining this not to actually be the case awkwardly shoehorned in five issues later