The first of the charity-funding We Can Be Heroes variant cover campaigns was to have been Justice League #12. However, because the program was decided upon at the last minute, that issue wasn't solicited through the usual channels. and orders may have been lower than expected.
Which is presumably why DC Comics have cancelled the blank variant cover of August's Justice League #12, in favour of next month's Batman #0, which has been solicited through the standard Diamond Comic Distribution system and is more likely to launch the program, which will see a new blank variant every month. They will raise money for those affected by drought in Ethiopia, Kenya and Somalia.
The final order cut-off date for retailers to order Batman #0 We Can Be Heroes blank varinat is Monday.