MSI will show off its Graphics Upgrade Solution at Computex, it's an external graphics card that connects to your laptop via an ExpressCard device. The Game Upgrade Solution will be sold in a bundle with the Radeon HD 5670 for between $169 - $229, but you'll also be able to buy the Game Upgrade Solution on its own for just $99 - $109. You won't be able to use a faster card though, you're not only limited by the ExpressCard interface but also by the power adapter which delivers a max of 84W. Future versions will use a USB 3.0 interface, but given all the limitations I think this will remain a pretty small niche market.
More info at Bit Tech.
When you consider this is all being pumped through an ExpressCard slot that has the equivalent to PCI-Express 2.0 1x bandwidth, arguably anything faster would be entirely wasted anyway. This ExpressCard interface was always the limitation on previous incarnations of the external graphics concept, and MSI claims to have worked to make the most of what bandwidth there is. For starters, it uses a thicker, shielded copper cable and with the "improved" associated electronics inside it means that the connection can use "over 70 per cent" of the theoretical bandwidth, unlike ~50 per cent or less from other ExpressCard devices. Future generations will use a simpler USB 3 interface, MSI claims.