At the moment the biggest problem I see is that the niche CoE3 player base is actually a subset of the niche Dom3 player base. A niche of a niche.
The MP of CoE3 pretty much sucks unless you are hotseating or maybe blitzing in IRC. CoE3 is much better for solo, better AI, and supports scenarios. But its hard to get a subset of Dom3 diehards who want that. Many of them try it and are unhappy at the non-Dom3ness of it.
On the other hand, it is on Steam. For years we have been promised that would give us the Steaming Horde of players. Im really hopeful of some NWNers or other migrants from scenario and campaign games.