For the web, we will keep this in context, do we really need to concern ourselves about supporting anything other then UTF8?
For example here is a partial list of character sets MySQL supports:
What do I find when I visit web shops?
The ones who either do not know anything about character sets, or do not care, just keep with whatever the default MySQL shipped with.
Otherwise? It is UTF8.
Unless of course they do not know, but it turned out it did matter. Those folks are typically sweating out a future where they know they will be altering all of their tables.
The question remains though, does it really matter? How about UC2?