If they're going to offer more than one model SP system, they'll have to use 45nm parts, as there's no 32nm replacements.
Now it's possible that they could offer a price reduction on them, but I wouldn't bet on it (it would cut into the LGA1156 iMacs, especially if it were $500USD).
They won't go with that many different CPU's. They currently only offer 6x total (3x per system; SP and DP). If they continue to keep it at this quantity, then there would have to be 2x 45nm Quads available. As per the DP systems, they could stick with 45nm parts to clear out any excessive remaining stock (they could have been caught with their pants down, as the contracts may have been signed before the economic meltdown). But if this didn't happen, then going 32nm would be what we see.
I do see 45nm as a posibility, assuming it was:
1. Planned (particularly to flush out the lines, as Apple would have been aware of Intel's intentions well prior to the public, and I'd expect that to have been before they even recieved shipments of the current parts).
2. Left over stock is really high.
I did some more reading and analysis this evening.
As per your comments, and what I've read elsewhere, the initial Gulftown desktop launch in Q1 will be limited to just one variant... the i7-980 at 3.3GHz. The i7-970 at 3.2GHz is not due until Q3. I couldn't find any info on Xeon parts but I guess we have to assume there will be a SP and DP Xeon equivalent to the i7-980.
Given the following existing price points:
Quad 2.66 -> $2500
Quad 2.93 -> $2900
Quad 3.33 -> $3700
Octo 2.26 -> $3300
Octo 2.66 -> $4700
Octo 2.93 -> $5900
Option A: Apple could just keep the lineup the same and inject the following Gulftown models at relative price points...
SP Gulftown -> $4500
DP Gulftown -> $6500

eek
Option B: Gulftown systems replace top-end Nehalems at old price points (more cores for the same money)...
EOL Quad 3.33 -> $3700 -> Replaced with SP Gulftown
EOL Octo 2.93 -> $5900 -> Replaced with DP Gulftown
Other models unchanged
Option C: Lower prices across the line, trim the lineup, and inject new Gulftown models (similar to my original proposal and what I'd do if I was Mac Pro product manager for a day)
Quad 2.66 -> $2500 -> $2200
Quad 2.93 -> $2900 -> $2600
Quad 3.33 -> $3700 -> EOL
New SP Gulftown Model -> $3500
Octo 2.26 -> $3300 -> EOL
Octo 2.66 -> $4700 -> $4300
Octo 2.93 -> $5899 -> $5300
New DP Gulftown Model -> $6000
Basically, I'd eliminate the top end quad in favor of a hexa core and eliminate the low end Octo which has no reason for living any longer and replace it with a new flagship DP Gulftown vessel.
Now if my pipe dream comes to fruitiion, then there will be a million threads titled "Should I get the 3.3GHz Hexa or the 2.66GHz Octo". I'm not looking forward to the endless debates on that front!

Actually, that would be a no-brainer in my opinion. Even if they were priced the same, I'd take 6 cores at 3.3GHz over 8 at 2.66Ghz any day. Hence my pricing on the SP Gulftown, can't be right.
So what's everyone betting on?