Yo as a pronoun, Ebonics

Children in Baltimore spontaneously invented a third-person singular gender-free pronoun.

So it turns out American English is actually diverging now due to cultural divisions.  AAVE (African-American Variant English) is a dialect getting some more intensive study - calling it "Ebonics" nearly led to the political death of all study of it, but it's a real dialect.  And it has some pretty fascinating grammatical differences from standard English, too, which just leads you to wonder how this language stuff really works.