In one of the D&D groups I play in, everyone has an iPhone (or an iPod that can use iPhone apps). Every one of us has at least 2 or 3 different dice-rolling apps. We've all used them at one time or the other. I personally use a particular app that comes with the sound of dice rolling -- it puts me at ease, makes me feel like I'm still rolling real dice.
So... I think the time has already come, as people I know are already doing it whether the rest of the people at the table are ready for it or not.
EDIT: while I'm at it, I might as well throw out an idea (again). If you've seen the iPhone app called Bump, you know that two iPhones near each other can swap/share data. I would pay money for an application that would have a minimal character sheet -- abilities, saves, AC, HP, attacks. And then the DM (or other players casting spells, for example) could "flick" modifiers to my iPhone. Thus, if the cleric buffed my fighter for 10 rounds, my iPhone would show my attacks with enhanced damage for those rounds. This isn't a dream-world app that might happen someday in a sci-fi future. It could happen today on iPhones if someone wanted to build it.