The new processors will be more expensive so prices will probably go up. Old processor prices won't come down so it is unlikely Apple will keep old models like they are with the Macbook (if that is what you meant).
New speeds available will be 2.66GHz, 2.8GHz, 2.93GHz and 3.2GHz. Apple will probably go with 2.66GHz on the low end and 3.2GHz on the high end then one or both of the others, probably the 2.93 if they only choose one. Airport might still be left off as it probably is only bought for a small percentage of Mac Pros. Display Port makes sense, but I wouldn't count on it.
Prices are likely going to be more not less because of LED backlighting. This is an area that is hard to predict because of the 24" being a bit of an odd thing in terms of how Apple have dealt with displays in the past. Personally I'd like to see a seperate pro line, but I can't see them doing two 24" displays.
You're probably right on all counts, the server/workstation cpus will be more expensive than current ones (at similar clocks) and the dual-quad 2.66GHz nehalem Mac Pro will probably cost $2999. But it doesn't negate the fact that this Mac will probably be faster than the current dual-quad 3.0 that ships for $3599.
The other thing is that it makes no sense what so ever to ship a single cpu model on a dual-cpu motherboard with the changes in the architecture. So, will Apple release two versions of the Mac Pro? Single cpu (X58 chipset and Core i7 cpu) and dual cpu (Tylersburg-EP and two xeon nehalems)...
Given the low price of the high-end desktop cpus (Core i7 965/940/920), Apple COULD release a single cpu Mac Pro for about $1299 (the quad 2.66GHz core i7 920 will cost about $284, the 2.93GHz $562, and the 3.20GHz $999).
Power requierements: a single Core i7 has a TDP of 130W, dual xeon nehalems cpus have a combined TDP of 190W or 260W for the dual 3.20GHz cpus. With each revisions of the Mac Pro the TDP increases. Maybe it's time to cool down a little.
So, here are my wishes (or better, the possibilities) for two lines of Mac Pro:
Uni-processor Mac Pro (X58 chipset, Core i7 cpus):
$1299 quad 2.66GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU
$1599 quad 2.93GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU
$1999 quad 3.20GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU
Wishful thinking, Apple would probably sell those for $1599/1999/2499 (if not higher), still I'd buy one or two of them...
Dual-processor Mac Pro (Tylersburg-EP chipset, nehalem Xeon cpus):
$2999 dual-quad 2.66GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU (the cpus X5560 will cost $958 each)
$3999 dual-quad 2.93GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU (the cpus X5570 will cost $1,386 each)
$4599 dual-quad 3.20GHz, 3GB RAM, 320GB HDD, Superdrive, nvidia GPU (the cpus W5580 will cost $1,600 each)