Though the engine appears quite robust they still have to implement most of the content.
Who says they haven't already? What do we know about SR's development schedule?
I am .. of course with some caution. You don't have to be a prophet in order to male an estimate now.
First of all, considering there is no publisher, it's quite likely that the alpha is presented at the earliest possible time. These guys are really enthusiastic and the point were you are most excited and eager about showing your software is when you have seen it up and running for the first time, not 1/2 year later. It's extremely likely they have entered alpha not too long ago. The WL2 demo may have been yet another impulse to get a slice of the game ready asap. They only had to wait til they can show something that will get people excited, and does not crash. It does not have all the bells and whistles, but enough that people will praise it.
Going by their two presentations, they seem to be almost finished with their engine and the Editor, which will both speed up things from now. But at that point they would still have to put most of the content in the game, because things work in a certain order, and putting content togeher comes after the engine is ready (as long as your name is not Zsoltan from tortured hearts). They were showing the exact same mission on two individual occasions (the kickstarter update and the gamespot thing yesterday). Commons sense tells this must be the first / or one of the first missions, were everything is in place, not a sample of an almost finished software close to beta.
From that point onwards, am optimistic estimate would be: MANY more months til beta, then some more months for testing and balancing .. probably more of that than we think because people tend to slack off and get lazy at that stage, when the hard work is done. Considering all of that, even Christmas 2013 sounds a bit optimistic, though not completely impossible.
From what I've seen, I am just certain it will be
no later than Christmas 2014, they seem too far advanced for that
. All presuming that the final game will fulfil the minimal standards of an RPG and will not be a shallow affair that people finish in two or three evenings. I would actually be VERY concerned if the game would indeed be released in May, because that most certainly guarantees that it was rushed and will suck.