If its a straight optical shrink (its not but just for the sake of this arguement) you're going to shrink it down by about 30%.

Assuming that the die shrink causes the chip to clock on a percentage basis with a conservative clock of 3200 (which most do with ACC) We are looking at Deneb clock speeds of around 4200 - 3900 mhz overclocks (which is quite close to what we saw with early screenshot leaks.

Part of why I went with Deneb is the assumption that the i7s when they go retail will be highly limited by what they can clock to (similar to the Q9300 on a X38 or an X48 based chipset)

That being said a 3.5ghz i7 will get romped by a 4ghz Deneb IF the price is the same, all bets are off however if the i920 does 4ghz @ release on retail chips