65 episodes is actually a respectable number of episodes for an animated TV show, and even if Brave and the Bold could've continued longer, it still left an impact on those who watched it, particularly its nice take on Aquaman (Outrageous!). Not all animated shows are as wildly popular as DuckTales was, and that show reached 100 episodes back in the day, which wasn't all that common for even popular animated shows at the time when the usual number of episodes was around 65 at most in a common lineup.

I bet we'll see a new Batman show unrelated to DC Animated Universe before long as opposed to Superman because the suits currently think Batman is hot stuff and will bring them more money than, say, a Superman show would. The real question is how long any new show will last on the network before being screwed over by bad decisions of the powers that be, and that depends on whether the suits actually give shows proper time slots, actively market the show via advertisements and merchandise, and don't greenlight stuff only to cancel them later, the latter being a rather rampant policy which Beware the Batman and Young Justice (which were outside DCAU) among others have sadly fallen victims to.