Magic casting is associated with hands now, so there is no button for that (you didn't put one, but I'm leading to something here). They already explained that bashing and blocking is done with the same key (you press for block, hold for bash. Yes, this means that blocking MUST be done AT THE MOMENT you're about to get hit, or you won't get anything out of it). So RB and LB are open for use. Oh, yeah, and you can't block while dual wielding. That also opens up keys.
Left Trigger = Use left handed selection
Right Trigger = Use right handed selection
RB = Grab
LB = Sprint
Left Control Stick in = Sneak
Right Control Stick in/held = third/first person/vanity mode
Y = Journal
B = Jump
A = Select
X = Sheath/Draw weapons
Granted, sprint and sneak's positions may be swapped. It just depends on a few factors.
I totally back you up on everything you said except the DW part. They never said we can't block while dual wielding. So we have to wait and see. Sounds like a sound disadvantage to DWing but it hasn't been confirmed or even hinted at yet. Though it doesn't make since how you would block either now that I think about it hehe, unless power attacks are out hmy: