The engine is responsible for how you create the game, what means you can use. The better the engine, the easier it is to do things. The easier things are to do, the fewer faults there are. The engine also controls the capabilities of graphics, and many gameplay possibilites.
That's not really the case with Gamebryo. Gamebryo was pretty much only a renderer, and not a "full" engine like Source, CryEngine and so on. The cell system, the AI, the physics and lots of other things weren't related to Gamebryo. This way many of the games that use Gamebryo play and look very different, I mean, Oblivion and Civilization V both use Gamebryo, and they are very different games. While many Unreal 3 engine games are somewhat similiar in gameplay.
If they replaced Gamebryo with a new renderer, it won't really mean that much. Maybe they added the Umbra middleware or something for better performance, but I don't really expect much of a difference between the Gamebryo renderer and the new inhouse renderer when it comes to visual capabilities (the visual look is something else entirely and depends on the artists).
Forgive those of us who are questioning the definition of 'new'. Time will tell and you can say 'I told you so' all you wish if thats the case. But in defense of Gamebryo the engine did 'not' stop development in 2001 and the game bugs in OB and FO3 are not the responsibility of the middleware vendor. Bioshock 2 was built on Unreal 3.5 and it was unplayable before the 1st emergency patches. Did you blame Unreal and say it was rehashed POS from 1999? I've seen what Gamebryo is capable of and it was far more than what BGS or Obsidian implemented. That said lets fold our arms, sit back, and see what BGS has done.
Indeed, Gamebryo hasn't been standing still. It's been under constant development (well, until they fired a lot of people last year), and it seems like a lot of people don't understand that. It's like saying the Quake 1 engine and Quake 3 engine are the same thing.
Gamebryo Lightspeed was released last year, I don't think there is any released game that use it yet, but somehow it's "bad" already? Continuing on the example of Hel Borne, that would mean that the Unreal 4 engine is already bad too?