MSI thinks out-of-the-box with its third generation Graphics Upgrade Solution (GUS). It has external GPU enclosure that features a Thunderbolt interface and is able to support multi-monitor output. Previous iterations have never taken off but that could be due to inappropriate interconnectivity standards unlike Thunderbolt. Even prior to GUS, there were even earlier attempts made by MSI such as their Luxium in 2007; unfortunately that too didn't progress anywhere. With the popularity of Thunderbolt-enabled devices, we expect to see such devices to give added graphics computing power to Ultrabooks whenever they need that added boost to play games or perform some GPU-intensive tasks.
GUS is certainly a step towards the commercialization of such graphical solutions for the end consumer. Currently, such external graphics card enclosures like the Cubix GPU-Xpander tend to be marketed as commercial and enterprise solutions.