Re: Someone please explain why....
Plus, let's not forget about this: there is no batsuit, and Blake does not know that Lucius helped out Wayne. There is only that super computer in the batcave that Blake COULD just use to help out the GCPD and could just be a male version of Oracle from now on. The ending leaves so many options for the viewer to think of.
I would like to think Blake could be a successor, but another option is that they could just leave the Batman legacy "dead" as it is and Blake helps in other ways.