British magazine SFX has an interview with Dan Radcliffe:
By the end of the series, at this rate, Harry will be a 6'5" 24 year old in a Hogwarts uniform. Although, admittedly, the rest of the cast are getting rather big now too! "Rupert is about 12'4"!" Radcliffe joshes. "No, how tall is Rupert now?" About 5'8"? Or 5'5", 5'6". I'm 5'4" and he's a lot bigger than me. Rupert and Emma are definitely going to be in the next film as well, and so it'll be great because we're all coming back. But Rupert has grown a lot. Emma is taller than me by about half a millimetre!"
Much thanks to Veritaserum for letting us know about the interview, and you can read the entire thing at their site.