There doesn't seem to be any official announcement on this, but it's right there in the solicitation: James Harren will be taking over from Becky Cloonan as the artist for Brian Wood's Conan the Barbarian for issue 4. Brian Wood Tweeted that Cloonan will do issues 1-3 and 7-9, and "after that we don't know yet." That's interesting, because Wood and Cloonan were definitely presented as a team, but Cloonan is busy with a lot of things, so who knows.
Anyway, for those who are not familiar with Harren, iFanboy has a short introduction to his work as well as a generous array of samples. As they point out, he has been a professional comics artist for less than two years, having started out with a short story for an X-Men anthology and moving on from there to other Marvel and DC projects before finding his feet in the Mignolaverse at Dark Horse. Cloonan's new look for Conan has gone down well with a lot of fans, but Harren looks like he will be bringing some interesting visuals of his own to the series.