There is nothing like a death blow in IT. The day might come that new sites don't use flash, but it will remain like everything.
Every time I read about the "death of something" in the IT I have to laugh. There are always companies that build something on a technology and it will be supported for long years and even remain if not.
New systems might make use of new technologies, new ways to develop, new whatever, but that does not remove what it there.
Companies like Youtube or Google might be quicker as their business model depends on it, but there is more.
Juergen