The Dragon Age team wanted it back themselves and made the decision to include it "well before E3" apparently. They didn't mention it at the time in case things didn't work out.
The removal of multiple race selection in Dragon Age II left many disappointed as only character class was offered. The nature of DAII's story forced players to remain human.
"Because we moved the date we were able to bring it back," executive producer Mark Darrah explained to GameInformer. "We basically just had the time necessary to bring it back." It won't be exactly how BioWare delivered multiple races in Dragon Age: Origins, which included a short prologue for each race; we just get to choose race.
The new release date for Inquisition was announced at E3 along with a new trailer. "Why didn't we bring it up?" said creative director Mike Laidlaw. "We wanted to make sure it was locked down; we wanted to make sure our homework was done so we could commit to it and people could, with absolute enthusiasm, get ready for elf or dwarf or whatever."
So far only Elves and Dwarfs have been shown as selectable races beyond Human, but BioWare is mulling over the possibility of the Qunari. Each of the races is treated differently with Elves in particular being treated little better than servants or slaves, which carried significant impact in the original DA: Origins.
Dragon Age: Inquisition releases on PC, Xbox 360, PS3, Xbox One and PS4 in Autumn 2014.