Not to invite people to yell at me, but... For my 2 cents, multiplayer functionality is secondary to making a fun, interesting game that people want to play. For me, for the moment, Elemental is pretty boring. It tantalizes only as long as you don't know the game logic behind what's happening on the screen. Once you work it out, you quickly find the mechanics to be childishly simplistic, stilted and/or artificial (not all at once but in turn for various features), and the game world sandbox created for you to play in to be lifeless, drab and boring. Many systems which might be interesting turn out to be underdeveloped, requiring more work to realize their potential (i.e. to be interesting/fun). Until these pretty fundamental problems are dealt with, there is not much of a game worth playing, single or multiplayer, so the question of rushing multiplayer out the door would seem to me to be moot.
That being said, it is important to keep in mind that Elemental is eventually intended to be multiplayer, and that fact creates consequences for the design and implementation of the rest of the engine. That can not be ignored. The work for making Elemental multiplayer has probably largely been completed at this point, so we're probably not talking about a major undertaking of new code on Stardock's part, but more of a packaging, polishing and testing effort, which is much less demanding. For continuing a sense of momentum and keeping people tuned in and interesting in Elemental, that could be a very good thing.
Personally, I'd work on the core game, "were I Brad". Which probably sounds like a funny thing to say. Alternatively, Stardock could focus on getting out the core of the modder's tools, so that the modding community could make an interesting game on top of Elemental. Either of those two focuses seem reasonable to me. From my perspective, multiplayer is a side show, at this point.
My apologies in advance to those whom my comments may have incensed. Just my perspective.