According to Engadget, a ‘reliable source’ has provided them with details of the second-generation (3G) iPhones firmware – which has apparently leaked to certain carriers early.

After significant dissecting of the devices firmware, Engadget state that tri-band HSDPA (3G) and GPS/Sat Nav is absolutely confirmed. Here are all of the technical details:
Infineon PMB6952 / S-GOLD3 six-band UMTS / HSDPA transceiver
Murata LMRX3JCA-479 tri-band amplifier (probably for 3G)
Sony SP9T antenna switch for GSM / UMTS dual mode
ARM 1176JZF-S – Main CPU (same as in 1st gen iPhone)
Skyworks 77427 chip – UMTS / HSDPA tx 1900MHz, rx 2100MHz
Skyworks 77414 chip – UMTS / HSDPA 1900MHz
Skyworks 77413 chip – UMTS / HSDPA 850MHz
Internal build model number: n82ap (1st gen iPhone was model m68ap)
UMTS Power Saving option – on or off
Just one more day to go until Steve makes an announcement – make sure you check back around 7pm UK time tomorrow!