I have been hearing people say this for a very long time, but I've never seen good evidence that it was true. I mean, at any point in time, the state of the art has "run into the laws of physics" - that's why it's the state of the art. At any given moment, the best we can do is limited by some physical property. Processors don't get faster because Intel just decides to turn the clock speed up. They get faster because researchers find ways around the old physical limitations.
And I think that's the fundamental misunderstanding people have about Moore's law and similar consistent growth trends. People see a consistent curve and they think "Oh, this is just the natural course of progress, and so it shall always be." But that's not how it works. The reality is that each point on that curve is the result of team of very smart people making a breakthrough.