"There is an imperfect existing solution, with a problem, therefore we will ban the existing solution and move to a new, better one"

... should require extraordinary certainty in completeness of ones new solution before banning the previous.

There are very few times when the legacy method should be deprecated, and Google is the poster child of someone who shouldn't be trusted to recognize them.

(Looks pointedly at Chrome mv2/3 hubris and implementation clusterfuck)