I heard a blip somewhere about Microsoft releasing Windows 7 in 2010. Maybe Vista will become was Windows ME is.
Early 2010 is the plan. Exactly 3 years after Vista.
For reference, XP was released about 13 months after ME.
While I believe there's at least a chance the Vista will be "orphaned" like ME, it's hard to compare the two situations:
-> Business had Win2K, but this time around, Microsoft is killing off XP despite huge demand. For "ordinary" consumers as well as businesses.
-> ME was, functionally, a crippled 98 with a shiny new front-end. Oh, wait... ;-). No, seriously, while Vista is crippled and does have a shiny new front-end, it's pretty far removed from XP and does have numerous security enhancements, although many of them sub-optimally implemented.
-> DirectX 10 further cuts ties with previous generation.
-> Lag time of 3 years for Vista -> Win7, compared to 13 months for ME -> XP.