We should be able to subscribe to wildcard tags with RSS (like c++*).
You can now get a feed of wildcards. At the bottom of a
/questions/tagged/ page (including wildcards) you'll see a RSS link (this isn't new), but the link handles wildcard's much better, for example this page:
Has a feed of:
Well, you can combine tags already.
(note that + has to be encoded if it occurs in a tag)