As Sharakkhal said, most indications point to PCI-E on P4 DTR (desktop replacement) notebooks by October, from Dell and Sager if not other manufacturers too.
As for A64 machines, it's all speculation right now, but PCI-E is due to hit A64 desktops sometime in Q4. Depending on how early that happens and the A64 notebook product cycles, we might see PCI-E on A64 machines early next year. If not Q1, surely by early summer at the end of Q2.
Centrino/Pentium-M machines probably won't get a GPU upgrade until the new PCI-E cards hit the platform with the Sonoma/Alviso early next year. They'll probably get a Mobility version of the upcoming X700 (RV410), current speculation has it codenamed M26 (compared with the MR9800(M18), X600(M24) and PCI-E version of the MR9800/X800(M28). The Mobile X700 could possibly have 8-pipelines, but there has been no solid info yet.
Here are a couple articles about the desktop version
of the X700, which the next Centrino Mobility PCI-E GPU will probably be based on:ATI's RV410 is the X700ATI RV410 'to ship in October'
Nvidia competition for the M28 (PCI-E MR9800/X800) is the 6800 core based NV41M
(also probably only for DTR, considering its power requirements) and the NV43M, based off the upcoming desktop Geforce 6600
, which probably will be coming to the next-generation PCI-E Centrino machines to compete with the Mobile X700 early next year.