A blog post from Yanick Roy on the official BioWare site confirms that BioWare Montreal is in charge of Mass Effect 4 development and that the game will use DICE's Frostbite 2 engine.
He also promises that it will be respectful of previous Mass Effect titles. "That evolution now takes its next step, with the news that the next Mass Effect game is already in development, driven by the team here in Montreal. This is the goal we have been working toward for years now, and every member of our team is proud, excited, and humbled to take on the responsibility for the next game." said Roy
He continued "There is really not much I can tell you about the game right now, except that it will be built with the amazing technology of Frostbite as its foundation, enhanced by many of the systems that the Dragon Age III team has already spent a lot of time building."
"The other thing I can tell you Is that, while it will be very respectful of the heritage built over the course of the first three games, with the original trilogy now concluded and the switch over to a new engine, we are exploring new directions, both gameplay and story on the fronts."
"You can still expect the pillars for the deductible is known to be fully intact though, including diverse alien races, a huge galaxy to explore, and of course rich, cinematic storytelling."
Well it certainly sounds like the Mass Effect series is in safe hands with a team that understand the nature of the project, only time will tell if the team will be able to deliver something that fans and newcomers with like.