It's been discussed ad nauseum if Darkseid will appear in Batman v Superman Dawn of Justice. With Batman "knightmare" we see what appears to be a Parademons which is the infantry of Darkseid.
There is also another picture supposedly from the dream sequence showing Darkseid's Omega symbol.
So,with information like this we will see at least a cameo of Darkseid if not a full appearance.Darwill tell you how,if Darkseid doesn't fully appear,how Batman will have this dream about the ultimate evil that is Darkseid. In the Comics, Darkseid made a cameo appearance via TV screen in Superman's Pal Jimmy Olsen 134 and 135. The next month,he made his first full appearance in Forever People #1. This is where the dream comes into play. The Forever People are 5 New Gods from the planet New Genesis. These New Gods are the ones who have fought against Darkseid's evil since time began. Basically, the New Gods are Heaven against Darkseid's literal Hell. Now, the Forever People were sent to Earth to defend it from Darkseid's forces. One of the Forever People is named Beautiful Dreamer. Dreamer can manipulate people's dreams to see future events and even make the dreams become manifest. This is one possibility, and the best answer, for why Batman is seeing visions of Parademons scooping up humans,a city in firey ruins, and Darkseid's Omega Symbol. If it plays out like this,we'll at least know where it came from. Darkseid is the baddest of bad guys and literally the God of Evil. HD even has beams that come from his eyes,called Omega Beams,that can disentintegrate a person or transport them to alternate dimensions. These Omega Beams,get this,literally lock onto YOUR SOUL, and you can't escape them.