The 'Warlords' are all the chieftains of the old Horde with Durotan being the only good guy. Some of the main heroes of the expansion are Velen (dunno if its Velen meeting himself or just past Velen), Maarad, Vol'jin, Thrall, Durotan, and some dwarf and tauren.
One mod recently post that "whatever leaks that claim new races or new classes are fake". Looks to me that it means there will be no new class/race. Iron horde Gronn, Arrakoa and their old god were also mentioned by other mods.
Mods have said they know no more than us.
Likely they are just saying that nobody has any idea and all leaks are fake.