There’s always the potential Suicide Squad 2, but Ben Affleck’s Batman movie would be the most logical choice.
It’s been confirmed that Deathstroke (played by Joe Manganiello) will be the Batman movie’s main antagonist, but that doesn’t mean he will necessarily be the only villain.
Jared Leto’s Joker debuted last month in Suicide Squad, but despite being heavily featured in advertising and marketing, he didn’t get that much screen time.
It’s been rumored many members of Batman’s rogues gallery will appear, so there’s no reason that Joker couldn’t have a supporting role, even if he’s not the primary bad guy causing trouble.