IGN AU has an interview with John DiMaggio who voices Marcus Fenix (and also Bender in Futurama) in the Gears of War series. In the Q&A, he confirms Brumaks, different characters and more.
"It's badass. In fact, I saw some of the stuff yesterday! Which level was it? It was, well listen, there's bigger beasts in this game. Bigger beasts. Remember the scene with the Brumak, when the Brumak comes out and we're like 'Brumak! Roll! Get outta there!' and it's coming after them – and they don't have a fight with him? Well, they fight him now."
He continues his enthusiasm towards the game, hinting that production has ramped up most aspects of the original tile. "Oh man, dude – there's new weapons, new beasts, there's a couple of new characters, and it's just badass."
A Brumak battle may not be new to owners of the PC version of Gears of War 1, but it will be completely new to those playing on the Xbox 360.