Actually the first CORE processor was technically the pentium 5.
Pentium 4 was the netburst architecture and the core was a totally different architecture. the Core 2 instead of having a high clock speed has lower clock speeds but simply processes nearly everything at a much faster rate than the first Core could.
I don't see Intel ever using the Pentium name again.
Also Quad core 2.5Ghz chips actually add up to 10Ghz. a 2.4Ghz quad core chip will set you back $275
http://www.newegg.com/Product/Produc...82E16819115017 overclock that ever so slightly and 10Ghz is already here....