At CES 2012 this week, MSI is demonstrating its GUS II, which enables a graphics card to be connected to a computer using a Thunderbolt connection.
The main limitation is that the graphics card has to be powered by the PCIe slot as there are no additional power connectors provided. Since the more powerful graphics cards require one or two additional power connectors this means you’re restricted to entry-level cards. Considering they are far better than what you can get with integrated graphics you should see a dramatic improvement in gaming and video quality.
MSI gave no estimate of cost or when they will be sold.