Depends on what might be included. I can see a "Best Voice-Over Performance" category becoming a reality, but it could include one of many things:
a) a voice appearing in a live-action film either as a narrator or as an otherwise unseen character (e.g. Morgan Freeman in "The War of the Worlds")
b) the voice of an animated character in an animated film (e.g. the aforementioned Matthew Broderick in "The Lion King")
c) the voice of a computer-animated character in a film heavily reliant upon "synthespians". This is probably the most contentious as in many cases the actor involved does more than the voice acting, and is often heavily involved in the character's physical performance too - the best example being Andy Serkis in "The Lord of the Rings" but this also includes the recent number of fully performance-captured, computer animated films based on an actor's physical performance such as Tom Hanks in "The Polar Express" - so there could be an argument for that performer to be eligible for the general acting categories, as many felt Serkis should have been back in 2002.
Going back 30 years, I guess Frank Oz as Yoda in
Empire Strikes Back would fall under "C" even though it's a hand puppet rather than performance-capture + voice acting; I think it's criminal that he couldn't be nominated for an Oscar, nor could Andy Serkis for either
Two Towers or
Return of the King. I guess they always could have given them a special Oscar if they were so moved, but that rarely ever happens.