Well, the logical answer is no, especially considering the title Paramount is working with is 'Five Brothers' (fairly impossible for a fifth brother to come out considering the plot of the first one, but who am I to quibble?), but it's potentially coming anyway. From The Hollywood Reporter:
Paramount is developing a sequel to its 2005 thriller "Four Brothers," bringing back many of the creative team for "Five Brothers."
Mark Wahlberg eyeing a return to star and hatched the sequel idea with original writers David Elliot and Paul Lovett, who are writing "Five." Lorenzo Di Bonaventura is back to produce.
The 2005 movie, directed by John Singleton, revolved around four adopted brothers (Wahlberg, Tyrese Gibson, Andre Benjamin and Garrett Hedlund) who come together to avenge their mother's death in what at first appears to be a random robbery. Although not a massive hit, it still grossed a tidy $74 million in domestic boxoffice.
Plot details are being kept under wraps, and it is not clear which of the other actors, if any, would return. Hedlund would appear to be out, as his character was killed in the first movie.
Wahlberg, repped by WME and Leverage Entertainment, stars in Peter Jackson's "The Lovely Bones" and appears in "Date Night" with Steve Carell and Tina Fey.
Elliot and Lovett, repped by Verve and Category 5 Entertainment, were writers on "G.I. Joe: The Rise of Cobra," Paramount's tentpole hit this past summer.