How do you know that it's the third Reformation rather than the sixth or tenth, Anastasia?
Oh, I'm not being dogmatic or trying to create some great theology about it.
Simply enough (really simply!)
I see the first Reformation as seeking to reform the Catholic Church. Result being a number of denominations that were similar in ways, but tried to correct what they perceived as errors in the Church, but maintaining Church itself.
I see the second Reformation as those having mostly seem to think the first Reformation didn't go far enough, failing to correct certain errors. Coming out of it with "a Church" in the ecclesiastical, authoritative sense doesn't seem to be their goal at all. Rather it seems more focused on the individual, perhaps divorced from a church, but at any rate, when there is a church, it's existence and authority is based on the individuals who make it up. Not the other way around. But the relationship of the individual with God, their salvation, piety, etc. is a strong central focus.
The emergent churches I've been to (admittedly few) ... well ... it's much harder for me to define. There is a nod to God, Church, and Scripture, (sometimes!) but really the central thing seems to be the individual. Not the individual and his own piety or relationship with God, as the second one I mentioned above, but the individual HIMSELF. God and all things related are seen more as a means to an end, which seems to be the happiness, well-being, social relationships, health, wealth, entertainment (etc ... in a devolving series of focus) - of that individual. The Church/pastor/Bible/God are a way to help the individual achieve various kinds of happiness and well-being.
It's so very different. So yes, I see it as a third kind.
That's just my own way of looking at it though, helpful to me. I'm not suggesting as a paradigm anyone else must follow. If someone else sees finer distinctions in earlier reformations and wants to make this one the 6th, or 10th, that's fine by me.