Last time i checked TotFW was an very air inspired raid? and al'akir is the freaking air elemental lord so i don't think we will see another air raid. An earth raid is not likely to come aswell since Therazane isn't interested in fighting with any one if just don't trespasses her realm. I think we likely only will have one more elemental raid after the firelands and that is the Abyssal Maw where we will help Neptulon fight back N'zath or something.
And another raid i'm pretty sure of will exist is the Caverns of Time raid where we will be brought back to the War of the ancients.