Nope, new expansion will be called "War of The Ancients" and will have Monk from diablo 3 as new class. Act 6 as well. Whole expansion will be what happens after world stone is destroyed and what the ancients have to do to stop hell from invading sanctuary to recover what remains of world stone and it's shards + the shards of diablos destroyed soul stone.
Will we get to save Cain from some shenanigans again in a6?