I would wait, it's a great game (concept) but it's just not done, or at lease until a demo comes out, as the above post said, if you got the $50, a big fan a 4X's why not but if your use to a finished product. I think in the long run you maybe disappointed.
I wish people would stop abusing words like 'great', 'beautiful', 'gorgeous', and 'awesome'. Elemental may be a good game, perhaps even very good, but there's no doubt it's not great. Which part of Elemental can inspire game developers ?
Elemental is a game from a practically extinct genre. It is perhaps good compared to its peers. But games like AoW:SM, Heroes of Might and Magic and especially Master of Magic appeared when there was big competition within the genre. MOM fought for the cult status it has. Elemental faces almost no competition.
Back to topic. I'm going to wait and see, I don't have money to spare anymore. Caution: Frogboy has said recently the first Elemental expansion won't be free for everyone, but only for people who buy the base game before certain (unannounced) date. So when the date is announced, that will be the final date to make the decision.