Intel remains tight-lipped about the clockspeed of its upcoming Nehalem processors but Bit Tech believes the fastest version will likely be a 3.2GHz chip:
Intel hasn't revealed the official speeds and model numbers for its new processor yet, but just about every machine we looked at was kitted out with a 3.2GHz processor... with model numbers masked away for the time being.
Even the Lost Planet: Colonies demo during Pat Gelsinger's keynote used a 3.2GHz Core i7 processor to compare performance side by side with a Core 2 Extreme QX9770, which is also clocked at the same speed. Now, I know he was talking about architectural advancements and improvements that Intel had made, but it all seems rather coincidental to me.
Of course, Intel will not officially comment on launch speeds at the moment, so we'll have to wait until either closer to the time, or indeed the Core i7 launch date to find out official speeds.