Basically, for applications, Flash becomes redundant since you need to use HTM for other devices anyway and HTML 5 supports everything important Flash does. For video, Flash becomes useless overhead, since you can just specify a codec already used in Flash which will save the user's processor and using Flash limits your audience to a subset of what just specifying a standard codec or two does.
Yes, except we are glossing over the part where you use a tool to "create" the application. Flash is a format AND an authoring tool. Unless Flash starts somehow exporting HTML 5, I don't really see this happening.
"Look! There! Evil!.. pure and simple, total evil from the Eighth Dimension!" -- Buckaroo Banzai