I think I read this in The Mythical Man Month but writing from memory:
Every software development project, no matter how well executed will produce outdated software. Said differently any software that is used is by definition outdated. This is simply, because unknown unknowns only become known unknowns during development.<p>Bitcoin is a perfect example of this. It might stick around for a while mainly because so many people are already invested in it, but when it comes to features Ethereum runs circles around Bitcoin. On the other hand Ethereum will probably never be fully finished.