Well, there's a couple of thoughts...
a) I will keep condemning the concept or premature fanfare. (various reasons)
b) good theory and might be very true
c) the new sprites could still be just the dev getting cold feet ahead of time, but well after making the game public. I'm not saying that's the reason definitely, but then again nobody can look into the dev's mind. Just a theory.
d) Yes, a huge success indeed.