The film is produced by J.J. Abrams, who also worked on the story with screenwriters Andre Nemec and Josh Appelbaum. Abrams directed the 3rd installment of the series, as well as last year's Star Trek, with Pegg in the role of Scotty, so this seems like their working relationship is continuing on.
It was reported last week that Tom Cruise is fully on board for the sequel, even if the studio isn't fully on board with him for it. Seems the poor performance of Knight and Day may cause some adjustments in MI:4 land, with the most heavily rumored being the addition of a younger, more bankable star as a new agent for Cruise's Ethan Hunt to train (for future sequel installments). My money's on Zac Efron.