Multiplayer was the most requested feature by players of SoD1. It was trumpeted across all those pre-release IGN streams, but sadly the reality is a disappointment. It is apparent that noone at Undead Labs really grabbed the idea of multiplayer and took ownership of it, so we are hobbled by the 'play it safe' multiplayer that was delivered. I firmly believe this is why player numbers are not where they could be.
True multiplayer where all players can become invested in one community they have built together, with everyone having access to build choices, resources, establishing outposts etc. That is what we were asking for during SoD1, and that is still what every player I know wants from SoD2. Maybe you need to go outside Undead Labs to find someone with the drive and experience to make this happen, but this is the feature I bought SoD2 hoping for and would have been able to bring in at least 3 other players if it had been delivered, and I know I'm not the only one.
I would buy SoD3 if it was a reskin of SoD2 with real co-op multiplayer, as long as you improved the maps. Don't take a backward step on the map again please.