It's not a hardware limit that keeps mobile from wholly eating desktop, but a software one. Mobile OSes are intentionally crippled and locked down at the OS layer. You don't own or control your device, and only approved software can run.
Android is a bit better than iOS in this respect, but not much.
None of the mobile vendors have any incentive to change this, since it would mean forfeiting the App Store tax and for Apple would cannibalize the Mac market. The only way I see an uncrippled mobile device entering the market that is high enough quality to compete is if someone with none of these conflicting interests bucks the trend. Android is pretty forkable, so a droid fork that solved the security problems in a non-feudal way and that supported the sort of docking you describe would be disruptive.
Dell? Compaq? HP? A "washed up" PC vendor with stagnant market share would have nothing to lose and might have the resources to pull it off.
Apple loves to canibalize itself. iPod, which used to be 50% of the company: practically gone, totally canibalized by the iPhone. The iPad has already eaten plenty of Mac, outselling it between 2:1 & 3:1. The idea that if only the iPad were less locked down it would sell more and canibalize the Mac, thus Apple doesn't allow it, is absurd.
The App Store "tax"? Sure, Apple doesn't mind the cash. But they are first, second and third a hardware company: that's where the real money is. The reason they have no intention to allow side loading apps on iOS has to do with user experience, eliminating support headaches and security (order may be different, but these re the reasons).
The fact is your dream device would appeal to the same people who buy desktop Linux machines now. They exist, but they are a tiny part of the market. Nobody can stay in business catering to just those customers.
Most people don't see the lack of control over their mobile devices as a problem. Instead, they see it as a good thing, because their mobile devices are a lot more worry-free than their computers.
Android is a bit better than iOS in this respect, but not much.
None of the mobile vendors have any incentive to change this, since it would mean forfeiting the App Store tax and for Apple would cannibalize the Mac market. The only way I see an uncrippled mobile device entering the market that is high enough quality to compete is if someone with none of these conflicting interests bucks the trend. Android is pretty forkable, so a droid fork that solved the security problems in a non-feudal way and that supported the sort of docking you describe would be disruptive.
Dell? Compaq? HP? A "washed up" PC vendor with stagnant market share would have nothing to lose and might have the resources to pull it off.