I would like to see the Barbarians and the Swamp faction; I'm used to them from Heroes of Might and Magic III. I want to see them in a new light! There will probably be something beautiful, especially for the Swamp faction!
The main problem with new-old factions like the Swamp and Barbarians is that players expect something really great from the developers, and everyone understands this in their own way. The developers, however, are not gods and may not create exactly what everyone expects. So, new factions are better in this regard – everyone has new experiences, and everyone is satisfied.