In Collider's interview with Snyder, he revealed that more 300 movies could be coming, but they might take an anthology approach and be set in different historical eras. That sounds kinda cool, actually, and there are plenty of battles throughout history where one side faced astronomical odds.
"We’ve been talking about is there a way, possibly, we move out of Ancient Greece and use it as a framing device for other conflicts that happened throughout history. I think I mentioned that we talked about the Revolutionary War version, and we talked about the Alamo, and we’ve talked about there’s a battle in China, a 'Lost Legion' kind of concept, any of those kinds of things are on the table."
Snyder has been chatting up a possible George Washington movie lately, one that would be done in the style of 300, and this is probably what he's referring to. It may sound ridiculous in theory, but how is it any different from other movies focused on specific battles? It's actually a clever idea that could extend the life of the brand well into the future, and if Warner Bros. is about anything, it's branding.