My first thoughts were
a) the Half-Blood Prince
b) the new DADA teacher
c) Godric Gryffindor's descendant
a) because it'd be a decent information, rather than that lion guy being some bloke Harry collides with in Diagon Alley; b) because there have always been new characters introduced as DADA teachers; c) because he's a... lion guy
and the Gryffindor symbol is a lion and a Gryffin or something is a lionlike... thing.
I don't think the book will be released in September '05. I would rather tend to say late '04, early '05.
Check
this out - they say she's halfway through book 6 and this probably doesn't
exactly mean she's written, like, 350 of 700 pages, but is pretty much done with the writing itself and is now re-reading and correcting everything.
Another interesting link and yet
another one.