In theory..sure.
In MY future reality..I don't think so. Two personalities in the mix of a romance are usually plenty enough. From what I have personally experienced in my long years of living on the fringe, someone participating in the polyamorous experiment is usually left feeling like a third wheel.
I would like to believe that it is possible for this sort of situation to work out, as the financial and household benefits would be enormous. Sadly, I think that most modern human beings are too selfish and territorial to cohabit in such a manner.
As for me, I like to keep my playmates and bedfellows separate from one another. It has caused problems in the past. Just because someone rocks my socks off, does not mean I want them to come live with me and my ol' man and keep house with us.
I've found that about 8 times out of ten (from my own personal experiences and those of friends), it's either the insecure female trying to KEEP her man who initiates the polyamorousness; or it is the man himself pushing her towards it, and she obliges because she is too weak-minded to voice her discomfort for the situation-- either that, or both of them have ABSOLUTELY no idea what the fuck sort of heartache they are potentially inviting into their lives. The remaining 20% are actually both completely into it. This is the sort of situation that should not be bungled into-- it should be well thought out, and all rules of the game COMPLETELY agreed on by EVERYONE.
Just my two cents. For those of you who are happy and well in this lifestyle, and successfully practice it, I congratulate you, but it's not for most people.