Jim at MarketSaw has found a small interview with Andy Serkis that ran in IndieLondon where he spills / confirms a few significant details about the first couple Tintin movies.

I'll just quote the same bits Jim did, since Serkis is as concise as can be:

Q. Are you going to be reuniting with Peter Jackson again for Tintin?

Andy Serkis: In fact tomorrow I’m flying out to start on Tintin. Steven Spielberg is directing the first one, and then Peter Jackson is doing the second. The bulk of the shoot starts in September but things got a little bit moved around after the writers’ strike.

Q. Were you at all worried when Peter first got back in touch that having played Gollum and King Kong, he might ask you to play Snowy the dog?

Andy Serkis: [laughs] Absolutely, in fact people assume that I am, which is even more disturbing [he’s playing Captain Haddock].

There we go: Spielberg first, Jackson second, Haddock obliquely confirmed. Very obliquely on that last point, since nowhere in the interview does Serkis actually identify his character.  

The detail that's missing: a name for the director's credit on the third film. The guessing games have been fun so far -- the best/most ridiculous name for the third flick to appear in the comments below gets a No-Prize.