Sonoma is the next generation Centrino Mobile Technology. The official release date from Intel is I believe around late January of next year, I think its January 17th, 2005. Here are brief feature summary:
Supporting Pentium M code-name Dothan processors with 533MHz FSB.
Dual-Channel DDR2-533(PC2-4200)
Serial ATA
PCI Express(this has to do with below this line)
Easier graphics card upgrade using Nvidia's MXM and ATI's Axiom technology
Wireless LAN with either Intel 2200BG or 2915ABG(Bluetooth?)
Intel High Definition Audio
Intel Next-Generation Integrated Graphics for Mobile(probably based on the Intel Graphics Media Accelerator 900 on the desktop 915G chipset but with some enhancements which one I believe is 400MHz core rather than 333MHz and using extra bandwidth of having Dual-Channel DDR2-533 since the processor doesn't need more than single channel DDR2-533)
More advanced power management functions, one being Next Generation Display Power Saving Technology(DPST).
Since you guys are getting a new laptop and the Sonoma release is not far away, might as well wait.
Sonoma will be faster than Centrino platform even though it uses DDR2 since mobile doesn't have low latency DDR RAM and high latency is DDR2's main disadvantage. Even so, DDR2 is better for mobile with lower power and easier frequency increase.