If your question is "Is it worth playing the prologue?" The answer is yes. It absolutely is worth it. If your question is "Should I wait for the game to start having updates?" The answer is that I would not hold my breath. If this game ever starts to release real progress I will be first in line to pay for it, but not before. If he releases what he has been talking about with the feature set he has mentioned in his updates I would even be willing to pay a triple A price point ($70-$80) for that. Just not until there is a product ready to buy.
Based on the notes from the author it is a classic case of over engineering. Instead of incremental releases, he claims to be working on a full drop of new content all at once.
For the record I am also eagerly awaiting the release of Winds of Winter. Any day now.