i wouldnt know much of the 45nm chips, but on the Ghz subject, Intel already broke 4 ghz, but the chip had heating issues and other bugs in general, so they couldn't release the chip for sale. Recently though, it looks like the only major issue holding the chip back is production. http://www.pcworld.com/news/article/0,aid,117176,00.asp
-Heres a PCWorld article on the subject.
AMD does theirs a different way, their chips are marked by what the chip can supposedly process at (compared to intel's ratings), which is why the chip is labled (for example) 4000+ , 2.4 ghz. The '4000+' is what it can supposedly process at (4 ghz) (compared to Intel) and the real clock speed (2.4 ghz).
Overall, the Ghz of a processor seems to be less important than it was a few months ago, as heating issues arose with such extreme speeds, the more popular thing now is dual cores. You will probably be more likely to see a tri or quad core processor long before 5 ghz processors appear.