Certainly not a forgotten concept. Flash itself was a highly disruptive technology: originally a vector painting engine created for mid-'90s pen computing, it sneaked under the radar for years under the guise of a harmless animation plugin.
Who could have foreseen in 1998 that Flash would replace not only Shockwave and Java, but also QuickTime and Windows Media on the web?
Sun, Apple and Microsoft had their lunch eaten without even noticing -- and they actively aided their fall by bundling the plugin in their products. ("It's only 100k, and advertisers like to use it for animated banners. How could it possibly threaten our business?")
IMHO, that is disruptive. In contrast, HTML 5 seems rather like a sustaining innovation that supports the existing business model of certain web giants.