I think you might be overestimating the amount of people that are going top dump their Desktops, laptops and platform to go use a tablet. Not everyone is on the move with their music stuff either. Even a laptop has a larger screen to work with. Storage? connectivity? etc etc etc. If you already have a bunch of gear that you have to move then a laptop is not that much of a hassle really and it has many advantages.
Android has a long way to go before it decides Microsoft are the bees knees and turns it’s toes up.
I agree with you to the extent that there is great potential there and the points you make are relevant. I just don’t think it’s going to be that fast or easy a decision for the majority of folk.