HTML5 has acquired new meaning, its definition has changed
That is categorically untrue. There is a W3C specification which defines exactly what HTML5 is (or more correctly will become).
The specification is a proposal, but this still doesn't mean that the term 'HTML5' is able to acquire new meaning.
This is because it's technical shorthand used to describe a group of technologies - and the group of technologies it represents can be specified precisely.
If most people use HTML5 to refer to all new and upcoming web technologies the meaning changes. One person using it that way is an error, nearly everyone using it that way changes the meaning. You can’t impose definitions top-down.
I know what you're trying to say - language is a fluid changing thing, which evolves.
While I agree with this concept - I don't think misuse of technical terms changes the meaning of those terms.
In this case, lack of education, misinformation and confusion are driving the misuse of the term. It won't change what HTML5 actually is, because we have an officially sanctioned definition.
HTML5 has become a very relevant term outside of technical circles and there it refers to all upcoming web technologies and – pretty much – always has. I guess you will just have to life with the two different meanings in two different context. I don’t think it’s a problem, I quite like HTML5 as a catch-all term for upcoming web technologies.
HTML5 [..] refers to all upcoming web technologies and – pretty much – always has.
HTML5 hasn't always referred to all upcoming web technologies. It's misuse is recent - and I think Steve Jobs has encouraged the change.
I find being asked for an 'HTML5' website problematic; a lot of clients use the term simply because they understand it's a buzz word - and don't actually know what they're asking for.
