1. I don't understand why you need to run 1080p on a phone.
2. Even decent cameras are not capable enough to record videos in HD quality, let alone phones.
3. I don't have any issues with multi tasking on current phones. You can pretty much open a few apps at the same time without any problems.
4. If you browse so much at once, you need a tablet or netbook.
I agree high end phones may be an extension of our digital lives. But you can't expect it to do things a PC can do. If you want to browse seamlessly with a gazillion tabs open, you need a tablet/netbook/laptop.
Sure you can hook up your phone to play videos on larger screens and a single core phone does that fine. But I don't expect it to play a 1080p file with 15mpbs bit rate and dolby 5.1, dts blah blah. I'm gonna need a HD player/HTPC for that.
A phone won't be able to replace every other gadget you have.
Even if we have dual core phones, we need the OS and software to properly utilize it completely.