This information I am providing here is pretty sketchy as it's based on a tweet that doesn't exist anymore. Simon Pegg, some time recently, wrote on Twitter that David Tennant has dropped out of the upcoming
Burke and Hare film and has been replaced by Andy Serkis. The tweet has since been deleted and i'm getting the info second hand, so if i'm wrong, don't sue me.
Burke and Hare is based on a real story about 19th century killers William Burke and William Hare who made money by selling cadavers to doctors by not waiting for people to die of natural causes, but sped up the process by just murdering them. It will be a mixture of darkness and comedy in the vein of the old Ealing comedies which director John Landis is a big fan of.
Police have released these sketches of what they think the killers look like. No-one knows why, as the case was solved over 150 years ago.

As you know, Landis hasn't made a film in a while so this is pretty exciting prospect. Sounds like it will be of a similar ilk to his Black-comic masterpiece
An American Werewolf in London, which is definitely a good thing.
source-http://www.collider.com/2010/01/20/it-is-no-longer-pegg-tennant-but-now-pegg-serkis-for-burke-hare/