But in reality voice limits input
Only if you have to talk to it like you're giving input to a computer.
Imagine instead that you're talking to a person, and not just any person, but a person who has the world's knowledge at his fingertips and knows you as well as a highly competent personal assistant. Rather than asking for your team scores, you'd say "Giants?" and you'd get back the most interesting points (to you) about the game. Follow that with "anything else?" and you'd get a rundown on the rest of the sports, focusing on the parts that most interest you.
Voice input with contextual awareness, understanding of the world, and personalization will blow away anything else in terms of input speed, accuracy and effectiveness.
Modern GUI's can present a lot more data faster than using voice to ask for the data
You're conflating two issues here. One is input, the other is output. Nothing is likely to ever be as efficient as voice for input. I'm a pretty fast typist and not a particularly fast speaker, but I talk a lot faster than I type, even on a nice full-sized keyboard. Output is a different issue. Text and imagery has much higher information bandwidth than voice. However, you can't always look at a screen, so being able to use voice output at those times is still very valuable.
Even now, I find my phone's voice input features to be extremely useful. Earlier today I was a little late picking up my son from karate. While driving, I told my phone "call origin martial arts". Now, I don't have an address book entry for Origin, in fact I've never called them before. But my phone googled it, determining that the intended "Origin Martial Arts" is the one near my home, and dialed the phone number for me. That's just the most recent example, but I use voice queries with my phone a half-dozen times per day because it's faster and easier than typing or because I'm doing something that doesn't permit me to manipulate the phone a lot.
Voice is the ultimate input mechanism for most humans. Right now it's pretty good (especially if you use Google's version of it; Siri is kind of lame), and it's going to get much, much better.