I like Gamebryo and I love Oblivion, so if TES V used Gamebryo, I would love TES V. Gamebryo doesn't seem obsolete to me, but why do people say it is?
MW has amazing graphics for its time, OB too, why not TESV when/if it comes out?
Gamebryo isnt obsolete, sure the one OB and FO3 are on is, but they wont use that same one for a TESV.
I know nif files and how to use them, I'd rather not have to relearn how to use a different format if they do change over... Im sure it similar case there, the Devs KNOW gamebryo, why switch over as has been said. They can use this system to its max potential, if they move over, they will need a LOT of time maybe a few game releases to really fully learn the new engine.
All the things that can be implemented may very well be by the time a TESV does/if it comes out. Look at MW and OB, top of the line, why should TESV be any different? Im sure they'll improve Havok and and some really cool features, if they leave something out like the rain through roofs thing, im sure they will have a reason for it as well, like as said, performance.