Fallout 4 is basically guaranteed to be at Bethesda's conference right?
Bioware is making ME4 though.
Nothing is guaranteed. Noone knows what they are doing. Maybe they just spent the last 4 years doing nothing!
.....or they have a demo of Fallout 4 ready to be shown on their stage closely being followed with a teaser which will reveal the release date on Microsoft's press conference.