No way that they'll have the Infinity War budget and timeframe-wise it makes sense for Diana to still be the "first" and clandestine superhero to appear in the modern world. Again, if they're still holding on to Man of Steel as the starting point of the DCEU.
To me, it's a bit more of how do they top themselves and build on Wonder Woman the film in the sequel. Sort of how the Lord of the Rings series of films kept building on each other, especially in their set pieces in each films's finale. The gods appear to be done with for a while, considering the defeat of Ares and the prior death of the Olympians. The Amazons appear to be lost to Diana. So what does that leave her with with Cheetah and Urzkartaga?
If they adapt the recent Barbara Minerva from Rucka's run, I could see a skirmish between Diana and Cheetah and Urzkartaga, his minions, and the Amazons. Perhaps Barbara will be the one who is intelligent and savvy enough to help Diana rediscover the Amazons and access Themyscira, allowing Cheetah and Urzkartaga to invade the island. Urzie does like his brides after all and would probably covet an island of incredibly powerful women.
Problem is we've kinda sorta of seen that before with the World War II soldiers in the first movie and Steppenwolf in the Justice League. While I'm guessing Urzkartaga will feature in the movie that kind of leaves us with a tritagonist-ish issue. Wonder Woman versus Cheetah versus Urzkartaga, which can be fun, but something we've also seen before (even with another feline fatale!) in Batman Returns with Batman, Catwoman, and Max Shreck. I guess that kind of situation is classic in storytelling and is often going to be repeated.
I'm also intrigued how they will display the concepts of feminism in the 1980s and how Barbara Minerva will feel their effects. And how Diana feels about the progress of feminism as she's been hidden and living in the world since the 1940s. I mean, is she annoyed by how slowly progress is being made compared to her life on Themyscira? Has she resigned herself to "this is just the way it is?" Why has she decided to to remain hidden? Does she feel more like an outsider now than when she did on Themyscira? Besides the antagonists in the film, there's a lot about Diana's inner life and choices that need to be explored.
Anyway, this is all guesswork and supposition of what might happen in Wonder Woman II, based on the pieces on the board we know about. I need to do some more thinking about how someone might approach Diana's story and villains in this situation in a unique, resonating way.