I saw Phonebloks a few minutes ago. My first thought is that it would experience the same problems that Linux experiences. It may be superior, but it takes a commitment to understanding what's better about it.
The average user doesn't care about the battery, processor, camera, etc. in their phone. They want a phone that works. There is definitely a subset of users that want to be able to customize their devices in the way that Phonebloks thinks is necessary, but I think that user base is too small to sustain the ecosystem they show in the video.
As a thought experiment, how many people are asking for the Galaxy S IV's camera module with the HTC One's processor attached to the iPhone 5's screen?
My guess is not many.