It'll be another year before Serial ATA starts producing any performance advantages over present ATA100 systems.
Again, AGP 8x will take a while before it starts being seriously used, most people don't see much difference between AGP 2x and 4x at the moment, and 4x has been out for quite a while.
I'd guess DDR RAM will come along for the AmigaOnes when G4 >1GHz CPUs come in (end of this year? total guess), but that's the only really important thing out of the things you listed
(The present A1s have ATA 100 don't they? If not, then that is the most important next upgrade)
Also bear in mind that future versions of AmigaOS are unlikely to double the minimum spec hardware like Windows does on each release :-)
Your A1 system *will* be much cooler :-) ... have you seen the max heat power outputs of the latest x86 CPUs? the P4 3GHz weighs in at 105W!!! Cook your dinner on that!
