Suggestion: if you want this to succeed, constrain your scope. Say No to touch-screen & voice! (IMO they are crippled interfaces compared to the keyboard)
If they want to reach a billion people then they're going to have to live in a world of touch screen (and maybe voice).
At NDC Oslo this year there was a keynote by Luke Wroblewski on user experience on the web. There's a video on Vimeo: http://vimeo.com/97305189
The key takeaway was that a significant percentage of people are using their smart phones with either only their thumb or their forefinger. Many people don't even have a computing device with a traditional keyboard and full-size screen. That talk got me thinking about this question: what would programming look like if you only use your thumb?
I don't think you can write off these interfaces, rather I think we may need to start to really think about separating creation of core components of software and then orchestrating the interaction of these components as a different aspect to developing software.
I've often wished I could program even a RAD proof of concept kind of thing on my phone. Many ideas come to me while I'm not at a computer (our desks are not always the most inspiring place we find ourselves) and as a consequence, are gone before I get back to work.
If you're wondering how programming with just your thumbs might work, look at Touch Develop from Microsoft Research.
It's worth noting that for programmers with some degree of RSI or a similar injury, a keyboard can potentially be a far less painful interface than a mouse or even touch.
Don't worry, we'll make sure it works whether you use the mouse, a keyboard, maybe even a touch screen or voice. :)