This is almost there...
1) Make it all windows, so that I have the same desktop/file structure/settings in tablet/laptop/desktop mode.
2) Make the desktop dock expandable with PCIe video card and SATA storage. (Even better would be CPU/RAM, but then you really have bought a whole desktop)
3) Incorporate with a game console so that game installs and save data can be stored on the tablet and played on any compatible console.
4) A pile of NAND with a fast bus
This would bring convergence, I would have one tablet that is a core module for my computing needs, and it would expand to the circumstances, I would not worry about syncing my tablet/laptop/desktop it would always be there, I just slot it into different form factors that match my current needs.
I want to play games - I dock to any compatible console, my game installs and saves are on the tablet, the console provides the CPU/GPU power to run them.
I need to run <productivity tool> - I put it on a workstation dock, and my <productivity tool> information is stored on the tablet to be used.
I need to type on the airplane - I dock the keyboard and go to town.
I want to watch a movie - I get to choose, I can watch from the tablet, I could watch from the PC dock, or I could watch from the TV through the game console.
But best of all, I could do this with any dock, I can take my tablet to my friend's house and play the new game I got just by docking with his console. I can travel for business and update my sim models on the other side of the world by plugging my console into a generic workstation.
Currently MS is the company in the best position to make this happen, they have the desktop OS, it is already convergent with the tablet OS, they have the Xbox waiting for this. Now they just need to stop screwing around and make it happen.