I think the Blueprints are very usefull to prototype ideas to have a quick result for evaluation, and to see how things affects the gameplay. That may boost portotype development enormously. Thats not questionable from my side.
For the prototypes that have been approved I would favour to turn them into C++ implementation to be safe on the long term. I would keep BP only for artwork and polish purposes, but never for game core components.
Because today, the BP are monlithic binaries not being mergable and not being viewable in a compare tool. They are very difficult to maintain. How to find the change causing the bug? And how to debug them? The BP binaries draws you back into the stone age of maintainability. On the long term, this will break the neck of a project, I am sure. But if UE4 will turn the BP persistence somehow into a readable script, the BP will reach a more professional level and being a way more applicable even on the long term for serious projects.
Today, from my point of view, the BP concept is welcome for prototyping, for skript kiddies fun project don’t caring about maintenance, and for artwork and game polish purposes. And, because the script kiddies from today may be the game developer of tomorrow, it is required to offer BP concepts to survive the market competition with other game engines like Unity. So that even is not questionable from my side. 
At MrGrr:
Yes, google has the license to print money, they are a kind of a sect of aliens, living in their own created reality. It’s pointless to orientate your needs on that aliens, if you are normal folk. I guess a google game developer has 2 UE4 supporter on each finger to guide him for pressing the right key and buttons.