Per Dell they will still be selling XP for at least a year. RTI is testing Vista now, they are doing V9 and then V8 though.
We think there are issues with the PROCS since they are still full DOS apps. We did some very basic testing of V8 on Vista and it seemed to run ok. But we didn't test anything besides install, make an invoice, make a voucher that kind of thing. And it was single station only.
HW vendors are going to give you that crap about selling only Vista, but they pulled that when XP came out too and they said were not selling 2000 anymore.
Reality is that businesses are slow to migrate to new OS's due to legacy applications and most don't move until after the first major Service Pack is released anyway. I checked and Toshiba and HP are still selling XP as well.