I'm not sure how many of the warlords that we'll end up seeing. The hardest part is that we don't know what they're going to do to the story. Unless they want to stuff in a bunch of silly narration at the beginning, I doubt they're going to include the Burning Legion in this story. I don't think Ner'zhul is even credited in the movie, so we're most likely just going to deal with his apprentice, Gul'dan. If I had to guess, this will be an incredibly condensed/distilled version of the WarCraft story. Gul'dan will most likely be the main antagonist, which he pretty much was in early WarCraft lore -- albeit, that was mostly in the shadows through his puppet Warchief Blackhand.
If I had to guess, we're mostly going to see Durotan, Draka and Gul'dan on the side of the Orcs. We might see side-characters like Drek'thar and Orgrim Doomhammer. (Doomhammer isn't that much of a side character in the lore, but for this story, he may be.) Keep in mind that Durotan's Frostwolf orcs are more shamanistic than most, and I'm expecting them (Durotan, Drek'thar, or both) to get a vision that Gul'dan will lead the Orcs to destruction. That's what will probably lead them to want to work with the humans to find a peaceful solution.