Well, realistically, I don't know of a time where really everyone saw it, but virtually everyone who mattered saw and wrote about the housing bubble for a long time. And it still was a bubble.

I recall seeing doomsday articles as early as 2005. It caught my eye back then because I had read irrational exuberance for the first time around 2001/2002, and my ears perked up when I saw the term being (re-)used more frequently to describe housing prices. For a considerable period before that, I only rarely came across that term in articles still mulling over the dotcom era.