Well, yes, because it isn't actually using an AGP slot, it is using its own little connector that is determined by Dell, that makes use of the AGP technology. Anyway, even now there are not even graphics cards in the desktop environment that can make use of PCI-E, at the moment, AGP is enough (more than enough in a lot of cases). Besides I think it will take about that long for PCI-E to move to notebooks.
To answer your question, yes you'll be able to upgrade as long as Dell continue putting out cards that will fit your notebook (i.e. quite a while) - you have to understand that it is not the same as a graphics card in a desktop computer. the actual Circuit board is made up of 8 sides and a curve, onto which the fan is built - it looks like the squiggle block from tetris - and connects to the motherboard at 3 different places electronically, and 4 places with screws; so you can't just go to the shops and buy a new graphics module, you will have to order one from Dell if and when they release a new model. (e.g. I could upgrade my D800 notebook from a GeForce 4 Go 4200, to a GeForceFX 5650 / MR 9600 Turbo / MR9700 because they are all the same form factor, and have been released subsequent to my notebook).
PCI-E will only begin to benefit us sometime into the future, and quite some time after that, only, will it begin to affect the notebook arena. At the moment, all it is, is a marketing slogan, and hype.
Regards,
RaPTuRe
Who's General Failure and why's he reading my disk?