Correct. They've already started selling the 4700's but still have 4600's available. The 400SC is essentially the server version (no OS, no onboard video, PCI video card) of the 4600 and is to be replaced, but I don't recall what their replacement model is.
The 8300's went OOS quickly as everyone snatched them up with the Northwood chips before the 8400's arrived in may time frame with just Prescott chips.
I havn't heard if they're dropping the 2400's yet for a 2500. I would assume they'll keep them around longer since they use the lower end chips (Celeron and < 2.66 P4) on 400 or 533 (200/266 DDR) busses, not 800 like the higher models. But the new Prescott based Celerons will be out soon, and actually are a LOT better than the Northwood based celerons.
Funny... Most everyone agrees for now Clock for Clock, a Northwood P4 is better than a Prescott (lower heat/power requirements) and that the Celeron based on a Northwood was abysmal compared even to low powered AMD chips (e.g. a 2.4 Celeron slower than a Duron 1.6) but from what I've read the new Prescott based celerons will be a good deal and will give AMD a run for the money, as they've doubled the L1/L2 cache and addressed pipeline issues.
Who'd have thought, it takes the low end Celeron to make the Prescott core shine.. (
www.tomshardware.com for more info)