Fear not, they are not swapping Peter Dinklage for Warwick Davis in the role of Tyrion Lannister (thankfully, as he's the best of the series!) This one belongs to the house Baratheon.
Prince Tommen Baratheon, now played with Callum Wharry on the left, will be interpreted by Dean-Charles Chapman on the right. Apparently, says io9, "this likely presages Tommen's rise to prominence in the wake of certain tragic events this coming season." Which tragic event that may be, you ask? Come on! It's easy to guess. And you know you are going to enjoy watching it so very much.