I really have to throw cold water over everyone banging on about how "It's the old engine". There have been some huge technical overhauls to it between Skyrim and Fallout 4, not the lease of which were worldspace DX11.2 shaders and upgrading to 64bit. The notion this is still the exact same engine as used in Skyrim or that because they're replacing elements rather than bulldozing everything and starting over is totally wrong. Hell, most people didn't have a clue that the Source engine is just a heavily updated 1996 Quake engine.
I strongly suspect when gamesas talk about the 'Creation Engine' they are probably only even referring to the most basic resource handling elements, not the graphics and certainly not the physics which is, (annoyingly) Havok. There are definitely areas where they can make significant improvements (shadows, scripting, shadows, reflections, shadows, specularity and shadows) but just 'changing engine' isn't a magic bullet.