Dell (Alienware) already sells the 2.53GHz mobile quad core part. http://www.alienware.com/customize/m17-notebook.aspx?SysCode=PC-LT-M17&SubCode=SKU-DEFAULT.
Acer and Apple are not the only ones.

I dont see the market for something like this unless the price point was sub $2k (laughs). With all the great values in the midrange notebook segment you would be foolish to get something like this unless you were using apps optimized for 4 cores. Chances are you are not. But hey it's apple, I'm sure a few users will want the "prestige".

Intel list Q9000 as a 2Ghz part.

The Q9100 is listed as a 2.26Ghz part.

The QX9300 is the 2.53Ghz part... and, as always, the X will mean eXtremely eXpensive.

http://processorfinder.intel.com/List.aspx?ProcFam=3040

http://processorfinder.intel.com/List.aspx?ProcFam=2967