It did take a few years after 2007 before it became obvious to pretty much everyone that the iPhone was going to be a huge hit but took a little while before some oddities in the original software were corrected and people adjusted to not having a physical keyboard which some thought was going to be a dealbreaker out of the gate.
Ballmer in 2007 also said the iPhone was not going to get any significant market share. It didn't even take close to fifty years, did it?