I think he was willing to share for multiple reasons. Firstly, he assumes he's done with the DC characters and just wanted to give fans a taste of what he had in mind. Secondly, after seeing Endgame its clear that both he and Feige had a lot of similar ideas on how to proceed with their franchises and if he were to continue, following through on his original intentions is unlikely as it would be seen as simply copying Marvel at this point.
If Snyder were to continue, I think an Injustice future is far more likely a direction to take as that seems to be what interests him the most and would definitely help set apart what DC is doing compared to Marvel. Time Travel would still ultimately have to play a role in this direction, however, but since its already been used once it would be a much different beast compared to how Endgame accomplished to save the day. Plus, with DC going full in with the multiverse with Flash, it allows them more wiggle room. I doubt Snyder will continue in any real capacity making DC movies, but I'd be lying if I wasn't interested in a potential Injustice movie at this point.