According to the Southern Institute of Technology (SIT), Bret is still set to act in the film as posted on Facebook last week (6th October):
Did you all see yesterday's Southland Times? Pg3, article "Character, personality land city starring role"... about how Robert & Duncan Sarkies are going to be filming "Two Little Boys" in Southland, described as a "bromantic black comedy" & set to star Bret Mckenzie, (Flight of the Conchords) & Hamish Blake (of Aussie comedy duo Hamish & Andy). Awesome!
As part of the project, SIT students will be offered the opportunity to work as interns on the film. Pre-production is expected to begin next month & filming to start in January.
Source: SIT Facebook page
Hamish is a naturally funny guy and is one half of 'Hamish & Andy'- a very popular Australian comedy duo. He isn't balding with a comb over lol but it would make more sense for Bret to play Nigel and for him to play Deano IMO, although it would be quite different seeing Hamish play such a character since he seems to be a very laid back guy in real life.
(Hamish is the one of the left)