The critics say the end is a little stretched and they think that's because this producer who also made the first one is resigning from the Harry Potter movies meaning this was his last one and he wanted to go out with a big bang kind of. That doesn't mean the movie series ends however. He's passing the franchise on to the director of Y Tu Mama Tambien I believe. That's the critics opinion though and we all know how those go
And for those who didn't hear, a couple weeks ago Richard Harris, the guy who played Dumbledore died so that'll be kinda weird in the third installment to have someone different play him...