In Fallout 3 and NV, your equipped weapon is displayed on your character (either "holstered" or in-hand) . . . weapons do NOT have to be assigned a hotkey slot to be displayed.
Of course, it was still just your equipped weapon, if I recall correctly. What some of these people seem to be looking for is a "I've got these four weapons hotkeyed, so my character is festooned with sheathes! I'm badass!" effect.
(Personally, I'm not a fan of that look, so if this system is in, I'll be switching weapons be going to my inventory every time. Until a mod comes out to change it. :shrug:)
------
edit: thinking about it, I think such a system would only work if there were a limited and pre-defined set of "weapon slots" to equip weapons in. Because there's only so many hardpoints you can define on a character without running into problems with clipping, weapon-draw animations, etc. So, instead of assigning weapons to general hotkeys, you'd stick three weapons in your weapon slots, with the three slots being something like Left Side of Belt, Right Side of Belt, and Back. With two-handers or bows only assignable to Back. Hmm, or two Back slots, so that you could have crossed swords equipped, or 2-hander and bow.
....hmm, and how would that work with dual-wielding. Complications.