The two simultaneous app concept is a very interesting idea. Chatting and working on or watching or reading something at the same time would be really neat in theory and the apps could be made to run side by side or stacked at half the resolution and that could all work out fine. And it would be neat to have one app running while flicking around a miniaturized version of your homescreen on the other side and launching something else.
Unfortunately, I don't think it'll ever happen, though for a couple of reasons. There's really no elegant way to perfectly divide the iPad's attention in all aspects. Processing wise, sure, two cores, but if you're esentially running two virtualiPads on one iPad screen, there are fundamental hardware issues, what does the home button control? Maybe a pop-up would ask if you want to quit one app/the other/exit two app mode? But then, what app do the volume buttons control, how does it handle sound from two apps generally, are you constantly tweaking the settings on apps so that's they're not both screaming through the speaker, muting one and favoring the other? Does the iPad do it automatically? Then, what if i want music going as well? Do they all just mute/stop each other in turns like what kind of happens now? Also, you'd basically be using two apps in portrait mode while the iPad was in Landscape or two apps in landscape mode with it in portrait, but some apps run only in one or the other and wouldn't jive well when used at the same time. I think ultimately it gets too messy in a lot of ways, you can solve the sound problem and still wonder how you'd watch a video and use another app that only functions in portrait mode. It would ruin the 'just works' factor a lot of users like about the iPad and throw everyone back into PC land wondering what's making that noise and calling their grandkids. People who are using the iPad as a laptop replacement are actually bending a little to how it works and changing their workflow to focus with intensity on one task at a time (taking care of all of my e-mail) and then switching apps to tackle the next task for a while (writing all of my blog posts). This is very likely how it will stay for the iPad going forward. And honestly, people could use a little less of a scatter-brained experience with computing anyway, at least I know I could.