In the comics, the next issue after Negan's defeat takes place about 2-3 years later in the New Beginning arc. I imagine the show will make a similar jump, maybe a little longer, allowing Judith to become more of a character. It's hard to say how far ahead FTWD is now. We don't know how long Morgan's journey took. Probably at least a month, if not two. The dreamlike sequences of Carl's vision of the future was basically a big easter egg for the time jump and new beginning. Basically when the show comes back, all the communities will have banded together to make a massive safe zone, with walker patrols and herd control, so the roads in between the communities are pretty much safe. No real spoilers there or anything, that should all be established quickly in the next season.